Ionizing-radiation beamline monitoring system

ABSTRACT

Embodiments are directed generally to an ionizing-radiation beamline monitoring system that includes a vacuum chamber structure with vacuum compatible flanges through which an incident ionizing-radiation beam enters the monitoring system. Embodiments further include at least one scintillator within the vacuum chamber structure that can be at least partially translated in the ionizing-radiation beam while oriented at an angle greater than 10 degrees to a normal of the incident ionizing-radiation beam, a machine vision camera coupled to a light-tight structure at atmospheric/ambient pressure that is attached to the vacuum chamber structure by a flange attached to a vacuum-tight viewport window with the camera and lens optical axis oriented at an angle of less than 80 degrees with respect to a normal of the scintillator, and at least one ultraviolet (“UV”) illumination source facing the scintillator in the ionizing-radiation beam for monitoring a scintillator stability comprising scintillator radiation damage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/332,047, filed on May 27, 2021, which is a continuation of U.S.patent application Ser. No. 17/091,310, filed on Nov. 6, 2020, which isa continuation-in-part of U.S. patent application Ser. No. 16/811,471,filed on Mar. 6, 2020, which is a continuation-in-part of U.S. patentapplication Ser. No. 16/697,439, filed on Nov. 27, 2019, which is acontinuation of U.S. patent application Ser. No. 16/529,200, filed onAug. 1, 2019, which claims priority to U.S. Provisional Pat. Appln. Ser.No. 62/714,937, filed on Aug. 6, 2018, to U.S. Provisional Pat. Appln.Ser. No. 62/815,006, filed on Mar. 7, 2019, and to U.S. Provisional Pat.Appln. Ser. No. 62/859,952, filed on Jun. 11, 2019. The disclosure ofeach of these applications is hereby incorporated by reference.

GOVERNMENT LICENSE RIGHTS

The invention was made in part with government support under one SBIR(Small Business Innovation Research) Grant (Number: 5R44CA183437)awarded to Integrated Sensors, LLC by the National Institutes of Health(National Cancer Institute), and two SBIR Assistance Agreements (AwardNos. DE-SC0013292 and DE-SC0019597) awarded to Integrated Sensors, LLCby the U.S. Department of Energy (Office of Science). The government hascertain rights in the invention.

FIELD

One embodiment is directed generally to radiation beam monitoring, andin particular to monitoring ionizing beams of particle or photonradiation while having minimal impact on the quality of the radiationbeam itself.

BACKGROUND INFORMATION

The most common type of radiation therapy for the treatment of cancer isexternal beam radiation therapy (“EBRT”). For this treatment, anaccelerator is used to generate and precisely deliver relativelyhigh-energy particle or photon beams from outside the body into thetumor. There are a variety of EBRT technologies, with the type ofradiation used falling into two general categories: (1) ionizingparticles such as protons, ions, electrons, etc., and (2) ionizingphotons such as relatively low-MeV gamma rays or X-rays. Ionizingphotons are the more common type of radiation employed for EBRT. Forparticle beam radiation therapy, in addition to protons, carbon ions andelectrons, other types of particle beams used or being investigatedinclude helium, oxygen, neon and argon ions, as well as low-energyneutrons (e.g., slow to thermal neutrons). Low-energy neutrons are used,for example, in boron neutron capture therapy (“BNCT”) and gadoliniumneutron capture therapy (“Gd-NCT”).

For both particle and photon EBRT, there are a variety of deliverymethods, including intensity modulated radiation therapy (“IMRT”),intensity modulated proton therapy (“IMPT”), three-dimensional conformalradiation therapy (“3D-CRT”), image guided radiation therapy (“IGRT”),volumetric modulated arc therapy (“VMAT”), pencil-beam spot scanning,pencil-beam raster scanning, helical-tomotherapy, stereotacticradiosurgery (“SRS”), stereotactic body radiation therapy (“SBRT”),fractionated stereotactic radiotherapy (“FSRT”), spatially fractionatedgrid radiation therapy (“SFGRT”), ultrahigh dose-rate flash therapy(“FLASH”), intraoperative radiation therapy (“IORT”), boron neutroncapture therapy (“BNCT”), gadolinium neutron capture therapy (“Gd-NCT”),etc.

SUMMARY

Embodiments are directed generally to an ionizing-radiation beamlinemonitoring system that includes a vacuum chamber structure with vacuumcompatible flanges through which an incident ionizing-radiation beamenters the monitoring system. Embodiments further include at least onescintillator within the vacuum chamber structure that can be at leastpartially translated in the ionizing-radiation beam while oriented at anangle greater than 10 degrees to a normal of the incidentionizing-radiation beam, a machine vision camera coupled to alight-tight structure at atmospheric/ambient pressure that is attachedto the vacuum chamber structure by a flange attached to a vacuum-tightviewport window with the camera and lens optical axis oriented at anangle of less than 80 degrees with respect to a normal of thescintillator, and at least one ultraviolet (“UV”) illumination sourcefacing the scintillator in the ionizing-radiation beam for monitoring ascintillator stability comprising scintillator radiation damage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a radiation damage recovery plot as a function of time (inhours) for 191 μm thick BoPEN film in accordance to embodiments.

FIG. 2 is a plot of the average pixel signal decrease as a function oftime for a 191 μm thick BoPEN film in accordance to embodiments.

FIG. 3 is a plot of the fluorescence light loss and recovery in air as afunction of time for different thicknesses of BoPEN film in accordanceto embodiments.

FIG. 4 illustrates an example of the Spread-Out Bragg Peak (“SOBP”) foran X-ray photon vs. proton beam in accordance to embodiments.

FIG. 5 is a plot showing the exponential fluorescence decrease asrecorded by the average camera pixel signal in accordance toembodiments.

FIGS. 6A-B illustrate two images of a 10 nA, 3.0 MeV proton beam insidea vacuum chamber in accordance with embodiment.

FIG. 7 is a projection of the camera field-of-view for the digital imagein FIG. 6A, taken at a working distance of 326 mm in accordance withembodiments.

FIGS. 8A-C illustrate a system that includes a two camera, singlescintillator beam monitor in a light-tight enclosure employing a rolledscintillator spool configuration in accordance to embodiments.

FIGS. 9A-D illustrate a system that includes a two camera, singlescintillator roll film beam monitor with linear translation of thescintillator spool system in a 6-way-cross vacuum chamber in accordancewith embodiments.

FIGS. 10A-C illustrate a system that includes a roll film scintillatorbeam monitor in a smaller 6-way-cross vacuum chamber without lineartranslation capability in accordance with embodiments.

FIGS. 11A-D illustrate a system that includes a singlescintillator-frame beam monitor in 6-way-cross vacuum chamber inaccordance with embodiments.

FIGS. 12A-C illustrate a system that includes a doublescintillator-frame beam monitor in a 6-way-cross vacuum chamber inaccordance with embodiments.

FIGS. 13A-C illustrate a system that includes a doublescintillator-frame beam monitor in a 6-way-cross load-lock vacuumchamber in accordance with embodiments.

FIGS. 14A-D illustrate a system that includes a two camera, two mirror,full-size single scintillator/window module beam monitor in a slimlight-tight enclosure in accordance with embodiments.

FIGS. 15A-C illustrate a system that includes a one camera, one mirror,half-size rectangular single scintillator beam monitor in accordancewith embodiments.

FIGS. 16A-C illustrate a system that includes a three camera version ofthe embodiments shown in FIGS. 15A-C in accordance with embodiments.

FIGS. 17A-B illustrate a system that includes a four camera version ofthe embodiments shown in FIGS. 14A-D for the full-size singlescintillator-frame beam monitor in accordance with embodiments.

FIGS. 18A-B illustrate a system that includes a four camera, full-sizedouble window/scintillator module beam monitor in a light-tight slimenclosure in accordance with embodiments.

FIGS. 19A-B illustrate a system that includes an eight camera, full-sizedouble window/scintillator module beam monitor in a light-tight slimenclosure in accordance with embodiments.

FIGS. 20A-C illustrate a system that includes a four camera, singlescintillator beam monitor employing a rolled scintillator spoolconfiguration in accordance with embodiments.

FIGS. 21A-B illustrate a two camera, full-size single scintillator-framebeam monitor without mirrors in a light-tight box enclosure inaccordance with embodiments.

FIGS. 22A-C illustrate a system that is a four camera version of FIGS.21A-B in accordance with embodiments.

FIGS. 23A-B illustrate 10 μs exposure camera images through a vacuumchamber window in accordance to embodiments.

FIG. 24 illustrates a 1 ms exposure of a captured image of a ˜2 mmdiameter proton beam irradiating an ultra-thin 12.2 μm BoPEN film whilemoving back and forth in a rastered zig zag pattern at 40 mm/ms inaccordance to embodiments.

FIG. 25 illustrates a four plate light baffle for air circulation inaccordance to embodiments.

FIG. 26 is a photograph of a 25×25 cm rectilinear image taken at a 45°tilt angle in accordance to embodiments.

FIGS. 27A-B illustrate the open central structure of a reduced/shortened4″ O.D. tube, 6-way-cross with 6″ diameter CF-flanges modified such thatthe total beam entrance-to-exit length is 5.9″ in accordance to vacuumchamber embodiments.

FIGS. 28A-C illustrate a system that includes a scintillator-frame beammonitor holding three separate scintillator films in a 6-way-crossvacuum chamber with a camera in an attached 4-way-cross open systemcapable of actively or passively cooling the camera in accordance withembodiments.

FIGS. 29A-B illustrate a system that includes a scintillator-frame beammonitor holding six separate scintillator films in a 6-way-cube vacuumchamber with a camera in an attached 4-way-cross open system capable ofactively or passively cooling the camera in accordance with embodiments.

FIGS. 30A-C illustrate a system that includes an eight camera, full-sizedouble window/scintillator sliding-frame module beam monitor in alight-tight slim enclosure in accordance with embodiments.

FIG. 31 illustrates a method to avoid loss of data during the readoutdead-time in a dual-scintillator multiple machine vision camera systemby introducing a time-delay in the camera sensor readout sequencebetween the two scintillator camera systems in accordance with oneembodiment.

FIG. 32 is a beam position, shape and intensity profile image using thesame 3.1 MP camera as used in FIG. 26 , photographed off an oscilloscopescintillator screen of an orbiting electron beam captured in 21 μs tominimize movement blur in accordance to embodiments.

FIGS. 33A-B illustrate a system and method in which anionizing-radiation beam source with two separated ultra-thinscintillator based multi-camera beam monitors can be used with a patientphantom or material cross-sectional phantom placed between them forpatient treatment planning, analysis and quality assurance including 2Dmeasurement of beam scattering, loss of beam quality/sharpness, and beamfluence as the beam penetrates the phantom for both single beam and gridseparated multibeam high spatial resolution radiotherapies (RT) such asminibeam-RT and microbeam-RT in accordance to embodiments.

DETAILED DESCRIPTION

Embodiments are directed generally to ultra-fast transmissive (“UFT”)two-dimensional (“2D”), high resolution, ionizing particle and photonbeam monitors primarily for applications based on, or related to,external beam radiation therapy (“EBRT”), including the monitoring in“real-time” of beam position and movement, intensity profile includingtail, beam fluence/external dosimetry, angular divergence and patienttreatment quality assurance.

In embodiments of the present disclosure, the term “ultra-fast” refersto “real-time” on-line monitoring and data analysis of streaming imagesof an ionizing-radiation beam within approximately 10 ms or less perimage, corresponding to a data analysis rate of approximately 100 framesper second (“fps”) or faster. For some embodiments, the streaming imagescan be coming in at rates of 1,000 to 10,000 fps (i.e., 1 ms to 0.1 ms)with the data analysis occurring concurrently. Further, the terms“transmissive” and “highly transmissive” are adjectives used to describethe relatively small amount of energy that a particle or photon loses intransit through a given material or system, which will be different foran entrance or exit window as compared to the scintillator materialitself as compared to the integrated beam monitor system comprising theentrance window, exit window, scintillator, and the column of airbetween the entrance and exit windows. For any given system the relativeamount of energy loss will vary greatly at different incident particleor photon energies which can vary over many orders-of-magnitude, and fordifferent types of particles from neutrons to protons to carbon-ions,etc. For an EBRT application such as proton therapy using a proton beamhaving an incident energy of 210 MeV, the term “highly transmissive”would mean losing no more than about ≤1% of its incident energy intransit through the UFT beam monitor system (i.e., losing ≤0.2 MeV), butfor the exact same system at 80 MeV “highly transmissive” would meanlosing ≤5% (i.e., losing ≤0.4 MeV). For this example at the sameenergies, the term “transmissive” would mean at 210 MeV losing no morethan about ≤2% of its incident energy in transit through the UFT beammonitor system (i.e., losing ≤0.4 MeV), but for the same system at 80MeV the term “transmissive” would mean losing ≤1%, (i.e., losing ≤0.8MeV).

The beam monitors in accordance to embodiments incorporate thin andultra-thin scintillator materials (e.g., scintillator sheet or filmmaterial) and are capable of internal, frequent, self-calibration tocompensate for a variety of factors including system non-uniformityincluding camera sensor/pixel response, optical system distortions, slowdegradation of the scintillator material due to radiation damage, signaldrift due to temperature rise within the monitor enclosure, etc. Inembodiments, the term “ultra-thin” refers to both window (i.e., entranceand/or exit window) and scintillator materials having a thickness of≤0.05 mm, and the term “thin” refers to scintillator materials having athickness of ≤0.5 mm and thus also includes ultra-thin scintillators.

The integrated detector/monitor in accordance to embodiments has anintrinsic 2D position resolution in the range of ˜0.03 mm to 0.2 mm,depending on the application specification requirements, and is highlytransparent to the incident ionizing particle or photon beam, therebyresulting in minimal beam scatter, low to extremely low energystraggling, and minimal generation of secondary radiation. Embodiments,in addition to EBRT, can be used for the monitoring of low-luminosityexotic particle beams and/or high-luminosity particle beams generated byresearch accelerators for scientific experiments, industrial particleand photon beam monitoring for materials processing (e.g., high energyion implantation, food and medical sterilization, cutting and welding,etc.), materials analysis, non-destructive analysis, radioisotopeproduction, etc. Beam monitors in accordance to embodiments generally donot require a controlled atmosphere or vacuum environment for properoperation, although some embodiments have been designed for operation invacuum or controlled gaseous environments.

Embodiments for EBRT applications generally result in positioning thebeam monitor downstream from the accelerator exit nozzle in an ambientair atmosphere. However, other embodiments are configured to operatewithin the vacuum environment of the beamline pipe to optimize and/ormonitor the beam shape, intensity, position and beam focus prior toreaching the beam exit/nozzle or target region. Embodiments for EBRTapplications downstream from the nozzle incorporate a unique foldedoptical configuration to achieve a thin profile to minimize encroachingupon the confined and narrow space between the beam nozzle exit and thepatient.

Due to the ultra-fast response capability of the embodiments of beammonitors, they can provide sub-millisecond and even microsecond beamanalysis and feedback to the delivery system, thereby allowingcorrective actions to be taken if necessary. For EBRT, this capabilitycan potentially improve the treatment delivery efficacy and protect thepatient, especially for recent “FLASH” therapy applications. For nuclearand high energy physics, this capability can provide particletime-of-flight (TOF) information in the range of 50 to 100 μs, orgreater.

It is known to use a scintillator, including a plastic scintillator todetect ionizing radiation, coupled with an electronic photodetectiondevice to quantitatively measure the emitted photons from thescintillator. It is also known to use a digital camera to record thelight emitted from an irradiated scintillator in applications rangingfrom monitoring the beam shape and position of an electron beam, tousing X-rays irradiating a scintillator to evaluate the quality ofmechanical welds, to optimizing the beam delivery system used in protonbeam therapy.

In contrast to known uses, embodiments implement multi-camera foldedoptical configurations, such as 2, 3, 4, 6, 8, 10, 12 cameras, foradvanced beam monitoring systems that provide critical performance andspace-saving advantages such as extremely high spatial resolution whileminimizing encroachment on the limited space existing between the EBRTexit nozzle and the patient's body. Embodiments also includeconfigurations of relatively compact machine vision cameras with imagingsensors that can stream images live to a computer system that includes aframe grabber for real-time data processing and analysis, the use ofmachine vision cameras that can be programmed for application specificparameter optimization such as selection of exposure time, gray scalelevel (i.e., bit depth), acquisition control and frame rate, gaincontrol, black level control, gamma correction for pixel intensity,pixel binning, pixel sharpening, windowing down the area or region ofinterest to achieve higher frame rates for faster beam analysis.Embodiments further include the use of both single and doublescintillator configurations that can be integrated as part of an easy toreplace foil-window/scintillator module package, and rolledscintillator-film motorized spool assemblies for automated scintillatorfilm advancement/replacement that uses novel polymer thin filmscintillator materials such as biaxially-oriented polyethylenenaphthalate (“BoPEN”), biaxially-oriented polyethylene terephthalate(“BoPET”), polyethersulfone (“PES”), etc. that are intrinsicscintillators without the addition of fluor dopants. Embodiments includenovel designs for quick replacement of radiation damaged scintillatorfilm or sheet with new scintillator film or sheet without significantservice downtime and recalibration time associated with the scintillatorreplacement process, configurations for real-time beam monitoringsystems operating in a vacuum environment, configurations for beammonitoring systems operating in either a naturally circulating orcontrolled flow-through ambient air or special gaseous environment suchas an enriched oxygen gaseous atmosphere to possibly minimize radiationdamage by enhancing oxygen assisted radiation damage recovery,configurations incorporating actively cooled camera sensors for enhancedperformance and reduced radiation damage of the camera sensor element,configurations incorporating the addition of internal UV sources such asUV-LEDs and internal UV detectors such as UV-photodiodes and appropriatefilters such as bandpass filters to achieve internal self-calibration ofsystem non-uniformity and near continuous self-correction forprogressive scintillator radiation damage; real-time software correctionof optical system distortions, perspective distortions (e.g.,keystoning), aberrations and non-uniformities including camera imagesensor pixel defects and non-uniformity.

Embodiments include configurations utilizing 3-way tees or wyes,4-way-cross, 5-way-cross and 6-way-cross vacuum chamber configurationsfor beamline vacuum operation that allow the use of either two cameras,or two photomultiplier tubes (“PMT”s), or one camera and one PMT, or PMTreplacements such as solid state photomultipliers (“SSPM”) includingsilicon photomultipliers (“SiPM”), avalanche photodiodes (“APD”),single-photon avalanche diodes (“SPAD”), etc. Embodiments include highdynamic range (“HDR”) computational imaging and with the thinnestscintillator films have extremely low beam energy straggling withminimal generation of secondary ionizing particles and photons.

Embodiments achieve advantages in part by using a scintillator filmmaterial, available in continuous rolls (e.g., >1000 ft length) of about70 cm width and greater, and thicknesses from about 1 μm to 250 μm inconjunction with other components to achieve unexpected results withregard to radiation damage resistance, photon emission, and as a thinand/or ultra-thin film scintillator. Embodiments include designs to takeadvantage of the new thin and ultra-thin scintillator material which ishighly resistant to radiation damage, while being able to minimize andpossibly eliminate most problems having to do with scintillatornon-uniformity and time consuming scintillator material replacement andsystem calibration.

Embodiments include an innovative folded-optics design to minimize theproduct profile/thickness to within about 6-14 cm, depending uponscintillator and camera size and camera angle. Embodiments include aninnovative automated, internal, rapid calibration system using UV-LEDs,UV-photodiodes, and UV and VIS bandpass filters, with an estimated timefor system calibration of about one minute or less. Embodiments includemachine vision cameras that would typically stream images at frame ratesfrom about 10 fps to 40,000 fps.

Embodiments discussed below include an in-line beam monitor design (e.g.FIGS. 11-13 ) with fast, high gain photomultipliers (e.g., approaching1×10⁷), coupled with an efficient photon collection system and suitablescintillator and radiation source (e.g., highly ionized particles withan atomic number of ˜10 or greater, such as) Ne⁺¹⁰ capable of generatingat least ˜200 photoelectrons and achieving on the order of about 100 μstiming resolution, and possibly better than 50 μs timing resolution,which is critically important for time-of-flight (“TOF”) experiments.

Embodiments further enhance timing resolution for TOF measurements byincreasing photon collection, such as through the use of two PMTs orSSPMs in the opposite arms of a 6-way-cross instead on one PMT (or SSPM)and one camera, or improving the collection of photons from the frontside of a scintillator by depositing a reflective coating on thescintillator back side, or roughening the front collection surface of ascintillator to prevent total internal reflection.

Embodiments include multi-camera configurations (e.g. 2, 3, 4, 6, 8, 10,12, etc., cameras) with FPGA frame grabbers and software that cancompile, integrate and analyze streaming images in real-time of themoving beam, while correcting for optical image perspective/keystonedistortions, lens distortions, vignetting, scintillator non-uniformity,camera sensor pixel non-uniformity, defective and radiation damagedpixels, etc.

Embodiments include manual or motor controlled push-pull linearpositioners and/or rotary drives to advance fresh scintillator film asneeded into the incident beam active area. Embodiments include aload-lock vacuum chamber design to change scintillator films withouthaving to break the beamline vacuum. Embodiments include an ultra-thin,light-blocking beam entrance and exit foil and/or polymer window, bondedto a thin frame, that can also be bonded to the scintillator film orsheet material to make a simple window/scintillator replaceable modulepackage that can be dropped into a pocket in the beam monitor frontand/or back cover plate and calibrated within a minute or so withouthaving to open up the system enclosure.

Embodiments have a design based on two different in-line scintillators,one sensitive to essentially all particles and high energyphotons/gammas except neutrons, and the other doped with a high neutroncross-section isotope such as B¹⁰, Li⁶ or Gd in order to make it neutronsensitive. By digitally subtracting the image/signal of the firstscintillator from that of the second scintillator, the resulting secondscintillator image/signal will be primarily that of the neutron beam andcan achieve the high performance at low cost desired in a high gammadiscrimination neutron detection system.

Most known EBRT particle accelerators are designed for pencil-beam spotscanning, but a few systems are designed for pencil-beam rasterscanning. The beam monitor embodiments disclosed below are compatiblewith both types of pencil-beam scanning systems, with most configured tooperate downstream from the exit nozzle, but some embodiments have beendesigned to operate upstream of the nozzle in the vacuum environment ofthe beamline delivery system either in the patient treatment room orprior to the treatment room and switch house and close to theaccelerator. The purpose of such systems operating in the beamlinevacuum is usually diagnostic to facilitate beam tuning includingmeasurement and optimization of the 2D beam profile in the deliverysystem, whether for EBRT, or for nuclear and high energy physics. In allcases, the scintillator material should be an extremely thin film so asto be almost transparent with very little low energy straggling so asnot to degrade the beam in the process of measuring it. For suchapplications, the scintillator film in some embodiments should be lessthan 100 μm thick and possibly as thin as 1 μm.

In embodiments the scintillator film BoPEN is employed in thickness downto 1 μm, and in some embodiments this film is physically attached to arigid frame as shown in some of the 6-way-cross embodiments disclosedbelow.

Experimental results showed a 33.0% initial decrease in scintillatorfluorescence from a 191 μm thick BoPEN film measured almost immediatelyafter being irradiated for 5 minutes by a low energy proton beam thatresulted in a film dose of 59 kGy. Specifically, FIG. 1 is a radiationdamage recovery plot as a function of time (in hours) for 191 μm thickBoPEN film exposed at a proton dose rate of 0.20 kGy/s, for 5 minutes,corresponding to a total dose of 59 kGy in accordance to embodiments. Inthe left plot the relative light loss was measured almost immediately inair after exposure, while in the right plot the sample was kept for ˜21hours in vacuum before being removed and then measured in air. However,after a 19-hour period in an ambient air atmosphere, the fluorescenceemission in the left plot had partially recovered and the decrease wasmeasured to be about 19.7%, representing about a 40% radiation damagereversal/recovery in less than one day. As shown in FIG. 1 , most of therecovery occurred within the first few hours, but radiation damagerecovery in air can continue for many days and even weeks, albeit at amuch-reduced rate.

The above BoPEN film (density of 1.36 g/cc) radiation damage experimentsemployed a 5.4 MeV proton beam that was continuously irradiated for 300seconds at an incident beam current density of 2.4 nA/cm². Upon passingthrough the BoPEN film, each 5.4 MeV proton loses about 2.14 MeV. Giventhe above beam current and integrated exposure time, the BoPENscintillator film was subjected to 59 kGy of accumulated radiation dose(1 Gy=1 J/kg) absorption as calculated below:N=(2.4×10⁻⁹ coul/sec-cm²)*(6.25×10¹⁸ protons/coul)*(300 sec)=4.5×10¹²protons/cm²J=2.14 MeV/proton=(2.14×10⁶ eV/proton)*(1.6×10⁻¹⁹ J/eV)=3.4×10⁻¹³J/protonMass=(1.36 g/cm³)*(0.0191 cm)=0.026 g/cm²=2.6×10⁻⁵ kg/cm²Dose=(3.4×10⁻¹³ J/proton)*(4.5×10¹² protons/cm²)/2.6×10⁻⁵ kg/cm²=1.53J/2.6×10⁻⁵ kg=59×10³ GyDose rate=59 kGy/300 sec=0.20 kGy/s

For a transmissive particle beam monitor based on viewing and measuringthe beam via its effect on scintillator emission, the effect ofradiation damage can be quantified by equating it to the reduction inscintillator yield as measured by relative light loss (i.e.,fluorescence signal reduction). With respect to obvious visual radiationdamage, none of the more than 30 BoPEN samples irradiated to date, atdosage levels up to ˜60 kGy, have shown any visual signs of scintillatordiscoloration or surface degradation which was an unexpected result.However, BoPEN films have discolored at 400 kGy (see discussion belowand Table 1).

In estimating the acceleration factor in experimental uses for differentapplications, with proton beam therapy being of particular interest, anaverage conventional daily patient treatment regime delivers ˜2 Gy persession. So, the above test that delivered 59,000 Gy to the BoPENscintillator film in 300 seconds is presumably equivalent to the doseincurred in treating 30,000 patients. In other words, 1 second ofaccelerated irradiation in the 5.4 MeV test beam, approximatelysimulates the radiation received by the scintillator in conventionallytreating ˜100 patients (a lesser number of patients for FLASH therapy).Or viewed another way, if a typical proton beam treatment room canprocess about 30 patients per day, then 5 minutes of the aboveaccelerated proton beam test is equivalent to ˜1000 days of conventionalpatient treatments in a one-room facility. This degree of radiationdamage resistance, with no obvious visual sign of surface degradation ordiscoloration in an off-the-shelf commercial polyester film, under suchan aggressive, high rate, accelerated testing regime is an unexpectedresult.

FIG. 2 is a plot of the average pixel signal decrease as a function oftime for a 191 μm thick BoPEN film exposed at a proton dose rate of 9.2kGy/s, for 53 seconds, corresponding to a total dose of 490 kGy inaccordance to embodiments. The time scale is shown in terms of thecamera image numbers recorded at 2 fps of the BoPEN film while beingirradiated in a vacuum chamber. It can be seen that even at this highdose rate there is relatively little difference between the linear andexponential fits.

From the BoPEN scintillator test experimental results to date, itappears that at the above dose rate of 0.2 kGy/s that radiation damageis linear with exposure, up to rates approaching 10 kGy/s (as shown inFIG. 2 ). By assuming linearity, corrections can be made for theincreased radiation damage that occurs at the sample back surface bysupposing that the average value between the front entrance and backexit surfaces provides a reasonable estimate of the fluorescence comingfrom the sample middle bulk layer. In making this correction, the bulkfluorescence value from the sample center now becomes 22.2% greater thanfrom the back surface. Thus the measured back surface light loss valuescan be corrected to obtain a more accurate bulk fluorescence value bymultiplying the measured back surface values in FIG. 1 by 77.8%. Makingthis correction, the 59 kGy dose exposure which caused a 33.0% decreasein initial fluorescence and the 19.7% decrease in fluorescence after 19hours, respectively becomes a 26% decrease (i.e., 0.778*33%) in initialfluorescence and a 15.6% decrease after 19 hours.

Hence the measured rad-damage values previously stated and appearing inFIG. 1 are overstated by 22.2% for the 191 μm thick BoPEN films.However, for ultra-thin BoPEN films with a thickness of ≤25 μm, thecorrection factors would be <1% and negligible. Likewise, fortherapeutic particle beams with incident proton energies in the range of70-225 MeV, even for the thin 191 μm thickness BoPEN film, there is nosignificant difference between the dose received at the front and backlayers, and thus the surface fluorescence signal as measured using a 280nm UV-LED source (located behind the BoPEN film and 99% absorbed in thefirst 0.1 μm back surface layer) accurately represents the radiationdamage at these energies to the bulk material.

FIG. 3 is a plot of the fluorescence light loss and recovery in air as afunction of time for different thicknesses of BoPEN film, ranging from3.0 μm to 191 μm, after exposure to a 5.4 MeV proton beam in accordanceto embodiments.

As can be seen in FIGS. 1 and 3 , and in general for all BoPEN films,most of the radiation damage recovery in air occurs within the first fewhours. The differential radiation damage effect described above, forthick versus thin scintillator films, explains the apparent differencesin relative light loss shown in FIG. 3 . For example, in comparing themaximum 7.3% light loss for the 12 μm thick BoPEN film measured after 40minutes to the 17.5% light loss (from the back surface) for the 191 μmthick BoPEN film plotted after 40 minutes (i.e., dashed vertical line at0.67 hours), the two values agree within an uncertainty of ±10% (i.e.,7.3% vs. 7.9%). The calculation for 191 μm thick BoPEN film is asfollows:Initial adjustment for front surface light loss in 191 μmfilm=(1−0.444)*(17.5%)=9.7%Additional adjustment for difference in beam currentdensity=(1.10/1.35)*(9.7%)=7.9%

Further, in experiments there was excellent agreement from two different191 μm thick BoPEN samples, measured more than three weeks apart, usingsignificantly different beam currents. In particular, the initial 19.7%light loss in FIG. 3 , when adjusted for the higher beam current densityin FIG. 1 (2.4/1.35), yields an adjusted beam loss value of 35.0%compared to 33.0% in FIG. 1 .

In estimating the beam energy lost in transit through the film, and thebeam shape and intensity via its fluorescence profile, it is necessaryto know the BoPEN film thickness and uniformity. A convenientnon-destructive method for measuring film thickness and uniformity isvia the front/back surface reflectance generated by spectralinterference. This method can accurately measure film thicknesses overthe full range from ˜1 μm to 250 μm, and to within about ±0.1 μmaccuracy. For the films in FIG. 3 , the measured thicknesses were: 3.0,5.8, 12.2 and 191.0 μm, as measured by spectral reflectance in thenear-IR over the wavelength range from ˜1,000 to 1,900 nm.

The above data indicates that thinner BoPEN scintillator films appear tobe more radiation damage resistant than the thicker films (e.g., see the300 second plots for the 3, 6, 12 and 191 μm thickness BoPEN films inFIG. 3 at both 0.67 and 2.45 hours). This result is completelyunexpected and surprising, and counter intuitive to what was previouslyexpected. Explanations for this unexpected result include that radiationdamage recovery is significantly faster in the thinner films in air assuggested by the narrow dashed vertical line intersecting the thicknessfilm plots at 2.45 hours and the projections further out at 4-5 hours inwhich the radiation damage appears to be essentially fully reversed forthe thinnest films as compared to the 191 μm thick film. Anotherexplanation includes that radiation damage depends on the probability offree-radical interaction, or a multi-particle free-radical mechanism,and so the thicker films having a greater free-radical density at theexit surface due to dE/dx, also has a higher probability of single ormultiple free-radical proximity interactions. Other explanations includethat the thinner films have a faster and higher probability offree-radical migration and diffusion to the film air surface, andbecause the FIG. 3 measurements were all in air, the thinner films havea higher rate of oxygen permeation and diffusion, as well as singletoxygen escape. Being able to provide a verifiable mechanism to explainthe higher radiation damage resistance of the thin films is notnecessary, as the unexpected good news is that for BoPEN the thinnerscintillator films appear to be more radiation damage resistant (i.e.,rad-hard) than the thicker films.

In embodiments, in order to refine the above estimates for thescintillator dose exposure under more realistic clinical proton therapyconditions, an additional 20% scintillator dose can account for patientplanning and calibration activity, and weekly machine maintenance. Thisadjustment means that the previously stated estimate of 30 patients perday, at 2 Gy per patient, corresponding to 60 Gy per day scintillatordosage, might prudently be increased by about 20% to 72 Gy per day.Therefore, the above calculated 59 kGy of accelerated exposure at a testfacility, would be equivalent to 819 days of accumulated patient serviceassuming conventional irradiation treatment (i.e., not FLASH).

If a proton beam facility operates 5 days per week, then 819 days ofservice corresponds to 164 weeks which would be more than 3.1 years ofcontinuous service. Assuming a linear radiation damage model (e.g.,shown in FIG. 3 ), the previously revised measurement of a 15.6% loss inscintillator efficiency due to radiation damage (i.e., loss influorescence after 19 hours) would correspond to a 0.156% efficiencyloss every 8.19 days. However, since radiation damage recovery continueswell beyond 19 hours, then over the course of 8.19 patient treatmentdays the accumulated damage will certainly be less than 0.15%. Morespecifically, for a 5-day patient treatment week the accumulated protonrad-damage is likely ≤09% per week for the 191 μm thick BoPEN filmassuming a 2 Gy dose to the scintillator per patient.

FIG. 4 illustrates an example of the Spread-Out Bragg Peak (“SOBP”) foran X-ray photon vs. proton beam in accordance to embodiments. FIG. 4shows that the above estimate overstates the rad-damage to thescintillator, because 2 Gy to the patient does not equal to 2 Gy to thescintillator due to the SOBP. The SOBP means that if the tumor receives2 Gy, then depending upon such factors as the tumor density, thicknessand location, which determine the proton beam energy, the radiation dosedelivered to the skin, or scintillator will typically fall in the rangeof about 50% to 75% of the dose to the patient's tumor, and would beabout 1.0-1.5 Gy. Therefore, instead of the accumulated BoPEN rad-damagebeing ≤09% per week as estimated above, after correcting for the SOBP,the 191 μm thick BoPEN scintillator should suffer a rad-damage loss ofonly about 0.04% to 0.07% per week. This result is most surprising andleads to the unexpected conclusion that on a weekly and probably monthlybasis the rad-damage to a 191 μm thick BoPEN scintillator is practicallynegligible, and even more so if a thinner BoPEN scintillator can beused.

FIG. 5 is a plot showing the exponential fluorescence decrease asrecorded by the average camera pixel signal measured off of a 191 μmthick BoPEN film exposed at a proton dose rate of 460 kGy/s, for 33seconds, corresponding to a total dose of 15,000 kGy in accordance toembodiments. The time scale is shown in terms of the camera imagenumbers recorded at 2 fps of the BoPEN film while being irradiated by a3.0 MeV proton beam in a vacuum chamber. As shown in FIG. 5 , and Table1 below, at the highest measured dose rates, the radiation damage is notlinear with exposure but is exponential. This means that estimates madeat these high dose rates (e.g., ≥90 kGy/s) can be misleading inprojecting greater scintillator radiation damage than actually incurs atlower dose rates integrated over longer periods of time. In other words,if the accelerated test data has a significant exponential component,then the actual scintillator radiation hardness would be better thanstated above.

However, it appears that in the range of accelerated radiation doserates chosen for modeling the performance of both therapeutic particlebeams and for nuclear physics particle beam monitors (i.e., dose ratesof ≤9 kGy/s shown in Table 1), projections based on a linear modelshould provide a good estimate of scintillator performance and anycorrections for exponential behavior would be minor as shown in FIG. 2 .For example, at a measured dose rate of 9.2 kGy/s, the linearrelationship for BoPEN films still appears reasonable (see FIG. 2 )corresponding to delivering 0.5 MGy in just 53 seconds (shown in Table1), which is an unexpected result. Yet at dose rates of ≥90 kGy/s,deviations from linearity are major and calculations based on theassumption of linearity would be erroneous and should only be used forqualitative purposes. At these much higher dose rates, slow to moderatescintillator ablation begins instantaneously (see FIG. 5 and Table 1).

TABLE 1 Summary of MIBL Proton Beam Accelerated Test Results for 191 μmthick BoPEN Scintillator Dose Current Beam Beam Rate Density CurrentEnergy Dose (kGy/s) (nA/cm²) (nA) (MeV) (kGy) Rad-Damage ObservationsDate  0.11* 1.35 5.4 5.4 33 No discoloration. Minimal rad-damage,largely reversible* Dec. 18, 2018  0.20 2.4 9.6 5.4 59 No discoloration.Fluorescence loss mostly reversible Dec. 18, 2018  3.3 40 10.0 5.4 390Sample 16: Area darkening disappeared 2 months later Nov. 26, 2018  9.250 1 3.0 490 Sample 13: No ablation but 0.6%/sec fluorescence Dec. 18,2018 decrease  92 500 10 3.0 6,100 Sample 13: Immediate but slow surfaceablation Dec. 18, 2018 460 2,500 50 3.0 15,000 Sample 13: Immediate fastsurface ablation => deep hole Dec. 18, 2018 *Rate of 110 Gy/s withminimal rad-damage is well in excess of the 40 Gy/s rate used for FLASHproton therapy.

None of the BoPEN films receiving dosages up to 59 kGy (i.e., 300seconds with 5.4 MeV proton beam at a current density of 2.4 nA/cm²) andat a dose rate of 0.20 kGy/sec showed any sign of surface degradation ordiscoloration despite significant decreases in fluorescence due torad-damage as shown in FIGS. 1 and 3 . Both figures show that measurableradiation damage recovery begins in air almost immediately afterexposure and that this recovery can continue for days or even weeksafterwards. However in a vacuum environment, such recovery is eithergreatly reduced or delayed as shown in FIG. 1 .

Rad-damage induced darkening (i.e. yellow-brown discoloration) has beenobserved in a 191 μm thick BoPEN film using the 5.4 MeV proton beam at a10 nA current, with a fixed, non-rastered beam focused on a 0.25 cm²area for 118 seconds. The resulting current density of 40 nA/cm² yieldeda dose rate of 3.3 kGy/s and produced an accumulated dose of 390 kGy.This dose rate was 16 times greater than received by the 59 kGy doseirradiated sample disclosed above. However, when the 390 kGy dose filmwas viewed two months later, it was discovered that thedarkened/discoloration area had completely disappeared, so apparently atleast some visually damaged BoPEN films can self-heal/recover in air tothe extent that they no longer appear visually discolored.

In order to evaluate the dosage associated with irreversible physicaldamage (such as burning a hole into the film by proton ablation), a morestable fixed proton beam accelerator was used with a 191 μm thick BoPENfilm at a reduced proton kinetic energy of 3.0 MeV and with a muchtighter beam focus over an ablated hole area of 0.020 cm² (i.e.,diameter at hole surface was 1.6 mm as disclosed below), at beamcurrents of 1 nA for 53 seconds, 10 nA for 66 seconds, and 50 nA for 33seconds. At each beam current a series of images were recorded at ashutter time/exposure of 1 ms, and at a frame rate of 2 fps for allthree cases.

FIGS. 6A-B illustrate two images of the above 10 nA, 3.0 MeV protonbeam, having approximately a 2.68 mm diameter, irradiating a 191 μmthick BoPEN film inside a vacuum chamber in accordance with embodiment.FIG. 6A is the digital image recorded with a 1 ms exposure and the pixelimage resolution is 38.2 μm. FIG. 6B is a Gaussian fit to FIG. 6A with ameasured average σ=0.61 mm and 97% of the beam falling within a 2.2σradius of 1.34 mm.

The number of images recorded for the above experiment corresponded to89 images at 1 nA (see disclosure below), 133 images at 10 nA, and 67images at 50 nA, with the fluorescence pattern and signal intensityrecorded for each picture on a pixel-by-pixel basis as seen in FIGS. 6Aand 6B for the 1st image taken at a beam current of 10 nA. A completeset of pictures at the three beam currents were taken without breakingvacuum or moving the camera, and by sequentially increasing the beamcurrent after each set of images (i.e., from 1 nA, to 10 nA, to 50 nA)while the beam remained focused on the same scintillator spot area.Therefore, when the BoPEN film was finally removed after the last imageat 50 nA, the partially ablated hole/crater represented the sum totalfrom the three beam current doses piled on top of one another. Althoughthe 1 nA beam caused no obvious physical film damage, it did suffer a0.6% decrease in fluorescence per second of irradiation (i.e., slope was0.003, see FIG. 2 ).

As previously disclosed, the fluorescence decrease followed close to alinear fit as seen by the solid line in FIG. 2 (there were two deadperiods when images were not taken but beam exposure continued);however, the dotted line in FIG. 2 represents a best fit for anexponential curve which is very close to the linear fit. The linear fitin FIG. 2 corresponds to a current density of 50 nA/cm², a dose rate of9.2 kGy/sec, and an accumulated dose of 490 kGy. Since the 10 nA protonbeam at 5.4 MeV and 40 nA/cm² caused yellow discoloration/darkening at adelivered dose of 390 kGy, it is highly probable that the 50 nA/cm² beam(490 kGy) also caused discoloration of the BoPEN film although it couldnot be seen since the area was subsequently ablated.

In contrast to the 1 nA fixed beam at 3 MeV, the subsequent 10 nA fixedbeam suffered more than an order-of-magnitude larger, 18% decrease inits overall fluorescence in its first second of irradiation as comparedto its initial signal, which must be due to immediate surface ablation.Similarly the 50 nA fixed beam suffered a 43% decrease in its overallfluorescence in its first second of irradiation as compared to itsinitial signal as seen in FIG. 5 , and given its deep hole creation injust 33 seconds it can be considered a “fast” ablation.

FIG. 7 is a projection of the camera field-of-view for the digital imagein FIG. 6A, taken at a working distance of 326 mm in accordance withembodiments. The camera was a Basler acA720-520 um with a 50 mm FL,f/1.4 lens. As shown in FIG. 6A, images were photographed through achamber window of the 3.0 MeV proton beam irradiating the 191 μm thickBoPEN scintillator film in real-time, with the camera outside the vacuumchamber at an estimated working distance from the front of the cameralens to the scintillator film of ˜326 mm (as shown in FIG. 7 ).

As disclosed above, the very “first” digital image (1 ms shutter speed)taken within the 1st second of irradiation (i.e., at 2 fps and prior tosignificant ablation) at a beam current of 10 nA appears in FIG. 6A,which from the measured ablation area of 0.020 cm² at the top surface ofthe hole yielded a current density of 500 nA/cm² corresponding to a doserate of 92 kGy/sec. The fitted beam profile for the image in FIG. 6Aappears in FIG. 6B with a calculated a of 0.61 mm, and a FWHM of ˜1.22mm, corresponding to a 97% full-bandwidth radius of 1.34 mm (i.e., 2.2σ)with an area of 5.6 mm². From the previous experimental data of therapid drop in average fluorescent signal (i.e., 18% decrease within the1st second of irradiation), it's clear that at this dose rate ablationstarts immediately upon beam exposure. However, from the progression ofreal-time camera fluorescence images over the 66 seconds of beamirradiation, it would appear that the ablation rate was relatively slowcompared to that at the 50 nA beam current.

As disclosed above, an incident 5.4 MeV proton beam has adequate energyto pass through the 191 μm thick BoPEN film and exit with a residualenergy of 3.26 MeV. However, at 3.0 MeV the proton beam only penetratesapproximately 119 μm into the 191 μm thick BoPEN film. If the protonbeam current density is sufficient to cause ablation and start “burninga hole” in the BoPEN film, then as the ablation proceeds the beam willpenetrate further and further into the film, eventually exiting first atreduced energy and then almost at full energy once the hole has burrowedor punched through. Examination under a microscope confirmed that evenat the 50 nA beam current, the ablated hole did not go all the waythrough the 191 μm thick film during the 33 seconds of beam irradiation,which followed the prior 66 seconds of much slower ablation at 10 nA.

The total estimated beam penetration depth was about 150-160 μm, andencompassed a maximum surface ablation area of ˜0.020 cm², although thehole ellipsoid minor and major axes in the area of deepest penetrationat the hole bottom was measured to be much smaller at about 0.4×0.6 mm(0.002 cm²). Based on the ablated hole area surface dimensions, theassociated beam current density was 2500 nA/cm² at 50 nA, correspondingto an accumulated dose of 15 MGy at a dose rate of 460 kGy/sec (seeTable 1). At this dose rate, it is clear from the “average pixel signal”in FIG. 5 , derived from each 1 ms photo/image at 2 fps, that ablationstarted immediately upon beam exposure (i.e., within a half-second).This result can be compared to the previous results for the 5.4 MeVproton beam at a current density of 2.4 nA/cm², in which rad-damageoccurred almost three orders-of-magnitude slower as it took 300 secondsfor the bulk fluorescence intensity to decrease by 26%.

The ablated area/hole created by the 50 nA beam was elliptically shapedwith measured minor and major axes of ˜1.4 mm×1.8 mm, corresponding toan equivalent circle with a radius of 0.80 mm and an area of 2.0 mm².However the Gaussian fit distribution for FIG. 6A, as shown in FIG. 6B,corresponding to the 97% intensity full bandwidth has a beam radius of2.2σ. This larger fluorescent emission area of 5.6 mm² associated withthe 2.2σ radius encompasses about 97% of the fluorescent signal areashown in FIG. 6A, and extends beyond the ablated hole. The fluorescentellipsoid minor and major axis dimensions corresponding to the 2.2σradius of 1.34 mm is 2.34 mm×3.02 mm, and corresponds to the estimateddimensions in FIG. 6A, with the camera image of the ellipsoid areacontaining ˜3,800 pixels. It follows from FIG. 7 that each pixelcorresponds to a field-of-view image area of ˜38.2 μm×38.2 μm. TheBasler acA720-520 um camera used for the FIG. 6A image has a 720×540pixel CMOS sensor. It also follows that with the 50 mm focal length lensemployed, the working distance (“WD”) from the front of the lens to thescintillator was about 326 mm, with the sensor field-of-view being 27mm×21 mm as shown in FIG. 7 .

The maximum beam current and minimum beam radius in the vacuum beamlinepipe of a 250 MeV proton accelerator is typically ˜800 nA for asuperconducting cyclotron with approximately a 1 mm beam radius. Theassociated beam current density is ˜25,000 nA/cm². Under such conditionswith a 25-50 μm thick BoPEN film scintillator, the dose rate could be100-200 kGy/s, causing significant ablation of the BoPEN film andresulting in hole-burning within a minute or so. Good practice woulddictate that the film radiation exposure in any one spot be limited toten seconds or less.

For the above case of a 100-200 kGy/s dose rate, embodiments include a5-way or 6-way-cross vacuum chamber that is designed to allow the BoPENscintillator to be moved out of the beam within seconds after beingmoved into the beam to capture the required beam images. The proton beamimage in FIG. 6A at a dose rate of 92 kGy/s provides an example of whatsuch an image might look like. Although the BoPEN thickness in FIG. 6Ais 191 μm, as compared to only 25-50 μm in the 5-way or 6-way-cross, thecamera lens can be much closer to the scintillator in the cross than the326 mm distance in FIGS. 6A, 6B and 7 , so the solid collection angle ismuch greater to collect a larger fraction of the emitted photons fromthe thinner BoPEN film, and in addition a better light-sensitive cameracould be employed than used in FIGS. 6A, 6B.

The low-energy proton beam tests at 3.0 MeV and 5.4 MeV for the 191 μmthick BoPEN film scintillator as summarized in Table 1 above covered amatrix spanning roughly three (3) orders-of-magnitude for the criticalparameters of beam current density, absorbed dose and dose rate. Theresults of the described accelerated test program demonstrate theexceptional performance to be realized from the broad family ofdisclosed embodiments that have led to a wide variety of UFT (ultra-fasttransmissive) high-resolution detection system embodiments for real-timemonitoring of ionizing particle and photon beams. The targetedapplications for the described embodiments below, include not onlyproton therapy, but all other types of particle and photon external beamradiation therapy (“EBRT”), as well as beam monitors for industrial andresearch accelerators including those used in nuclear and high energyphysics, etc.

With regard to proton therapy, embodiments demonstrate an unexpectedresult that 5 minutes of testing at a beam particle energy of 5.4 MeV, abeam current density of 2.4 nA/cm², and an irradiation dose rate of 200Gy/s will not cause visual damage to the BoPEN scintillator, but wouldbe roughly equivalent to the dose incurred in treating ˜30,000 patientsassuming a conventional dose of 2 Gy per patient, or 3,000 patients at aFLASH dose of 20 Gy per patient. Thus radiation damage to a BoPEN filmscintillator is not a significant issue and can be readily handled asdisclosed below.

Given the previous estimate of 0.04% to 0.07% maximum accumulatedscintillator radiation damage per week in a “typical” treatment roomfacility seeing 30 patients per day, embodiments have a need to advancea fresh area of scintillator film to the scintillator isocenter on abi-weekly, monthly or possibly even quarterly basis; the latter periodcorresponding to a maximum estimated fluorescence loss of ˜0.9%.Therefore, as a practical matter it appears that having to measure thedaily or weekly rad-damage contribution to scintillator non-uniformitycan likely be ignored due to it being inconsequential, which hasimportant implications. Specifically, calibration efforts in embodimentscan be shifted to measuring and quantifying the other parameters thathave to be monitored for achieving and maintaining an integrated systemaccuracy of 1% or better on a per patient daily basis. It follows thatgiven the very small amount of rad-damage incurring on a weekly basis, astrategy of advancing the scintillator film, either by unwinding it froma spool (e.g., similar to advancing 35 mm film frame-by-frame in acamera) or by pushing a frame with the film mounted to it by a fewcentimeters on a periodic basis (e.g. weekly, biweekly, monthly, etc.)could be implemented via a variety of embodiments as disclosed below.

FIGS. 8A-C illustrate a system 800 that includes a two camera 840,single scintillator beam monitor in a light-tight enclosure employing arolled scintillator spool configuration in accordance to embodiments.FIG. 8A is a perspective view with the top cover plate removed, FIG. 8Bis a top view, and FIG. 8C is a section A-A view. The dotted arrows inall three figures show the direction of film movement from the feed rollto the take-up roll.

System 800 includes a two mirror 830, folded optical configuration whichminimizes the light-tight enclosure depth/thickness while incorporatinga mechanism for advancing the scintillator film 860 to minimize oreliminate having to correct for scintillator radiation damage. Arelatively thick scintillator film such as 125-250 μm thick BoPEN film(i.e., 5-10 mils) is wound onto a small diameter (e.g., 2.5″) feederspool 870 to an outer diameter (“OD”) that fits within the light-tightenclosure (e.g., ˜4″). This film could be of any width (e.g., 25-45 cm),and could contain a total length of about 20-25 meters of 191 μm BoPENscintillator. In this embodiment, film 860 would be pulled across anactive window area 812 onto a suitable take-up spool 872, and advancedby a stepper motor 880 that rotates the take-up spool spindle asrequired. An ultra-thin dark colored exit window 814, such as 15 to 25μm thick black aluminum foil, is shown in FIG. 8C, while one of theUV-LED sources 850 and UV-photodiodes 852 are shown in FIG. 8A, with thetwo UV-LED/UV-photocell combinations 854 shown in FIG. 8B.

FIGS. 9A-D illustrate a system 900 that includes a two camera, singlescintillator roll film beam monitor with linear translation of thescintillator spool system in a 6-way-cross vacuum chamber in accordancewith embodiments. FIG. 9A is a cross-sectional view looking from thefront with the scintillator film 940 positioned in the center of thebeam path by linear position translators 950 and with cameras 902 and904 in the top and bottom arms to achieve enhanced beam imageresolution. The scintillator film is wound onto and stored on a smalldiameter feeder spool 930 and pulled across the beam axis transit area970 (in FIG. 9B) onto a suitable take-up spool advanced by an internal(i.e. vacuum compatible) stepper motor 920 that rotates the take-upspool spindle as required. Also shown is a reducer nipple 990 that canconnect to an external pressure bleed and/or vacuum line (not shown) tobe used to break and then re-establish the beam monitor vacuum duringsystem isolation for scintillator replacement (see FIG. 9C descriptionbelow). FIG. 9B is the same cross-sectional view but with thescintillator film 940 translated vertically up and out of the beamlinepath region 970, by the linear position translators in their extendedposition 952. FIG. 9C is a perspective view of the closed system showingall 6 arms including the beam entrance and exit gate valves 912 and 910that can be shut to isolate the beam monitor system and allowscintillator roll access and replacement without breaking beamlinevacuum. FIG. 9D is a cross-sectional perspective view of FIG. 9C showingthe ˜45° scintillator film angle with respect to both the beam angle ofincidence and the viewing angle for both camera systems (also visible inFIG. 9A). It is noted that the 6-way-cross in FIGS. 9A-D is shown likeall of the other 6-way-crosses with each arm at a 90° angle with respectto its nearest adjacent arm. However, to improve the photon collectionangle/efficiency, one or both camera arms can be constructed atapproximately a 45° angle with respect to the main body of the6-way-cross housing the scintillator film so that the camera lensoptical axis is at approximately a 90° angle with respect to thescintillator film plane.

FIGS. 10A-C illustrate a system 1000 that includes a roll filmscintillator beam monitor in a smaller 6-way-cross vacuum chamberwithout linear translation capability in accordance with embodiments.FIG. 10A is a cross-sectional view from the front showing a camera 1004and camera lens 1006 in the top arm and a PMT 1060 in the bottom arm;the latter for fast timing applications with enhanced light collectioncapability via a set of condensing lenses with the top lens 1050 locatedin the vacuum chamber just below the scintillator film 1040 and thebottom lens 1052 located just above the PMT 1060 in an ambient airenvironment. As in FIG. 9A, the scintillator film 1040 in FIG. 10A is atapproximately a 45° angle with respect to the beam, camera and PMT. FIG.10A shows the two UV-LED/UV-photodiode combination assemblies 1080 onopposite sides of the camera lens 1006. The scintillator film is woundonto and stored on a small diameter feeder spool 1030 and pulled acrossthe beam axis transit region onto a suitable take-up spool 1024 advancedby an external stepper motor assembly 1020 that rotates the take-upspool spindle as required. FIG. 10B is a perspective view showing all 6arms including the beam entrance 1001 and exit gate valves that allowsystem vacuum isolation and subsequent pressurization through thereducer nipple 1090 (in FIG. 10A) for scintillator roll replacementwithout breaking beamline vacuum. FIG. 10C is a close-up cross-sectionalview showing the two UV-LEDs 1086 and 1088, and two UV-photodiodes 1082and 1084 on opposite sides of the camera lens.

FIGS. 11A-D illustrate a system 1100 that includes a singlescintillator-frame beam monitor in 6-way-cross vacuum chamber inaccordance with embodiments. FIG. 11A is a cross-sectional view showing4 of the 6 arms as seen from the front with a push-pull linearpositioner on the left and a vacuum reducer nipple on the right. FIG.11B is a perspective view showing all 6 arms of the closed systemincluding a gate valve attached to the beam exit flange. FIG. 11C is across-sectional perspective view showing the tilted scintillator frameat approximately a 45° angle to the beam, camera and PMT. FIG. 11D is aclose-up sectional view of the beam cross center showing a firstcondensing lens in the chamber vacuum region with the second condensinglens just below the viewport window in front of the PMT in an ambientair environment. Also just above the viewport UV window for the camera,on either side of the lens barrel are a pair of UV-LEDs and associatedUV-photodiodes.

FIGS. 12A-C illustrate a system 1200 that includes a doublescintillator-frame beam monitor in a 6-way-cross vacuum chamber inaccordance with embodiments. FIG. 12A is a cross-sectional view showing4 of the 6 arms as seen from the front, with a full-nipple and push-pulllinear positioner added to each side as compared to only one side inFIGS. 11A-D. FIG. 12A shows one scintillator-frame on the left side witha second scintillator-frame mostly on the left side but covering thebeam center. FIG. 12B is a cross-sectional view showing onescintillator-frame in each nipple with no scintillator in the beamcenter region. FIG. 12C is a perspective view of the closed 6-way-crossvacuum chamber. In system 1200, the scintillator-frame is at about a 45°angle with respect to the beam, camera and PMT.

FIGS. 13A-C illustrate a system 1300 that includes a doublescintillator-frame beam monitor in a 6-way-cross load-lock vacuumchamber similar to FIGS. 12A-C, but with the addition of two gatevalves, each positioned between the 6-way-cross body and the addedreducer tees which have replaced the full-nipples in FIG. 12 inaccordance with embodiments. The added gate valves convert thisstructure into a load-lock vacuum chamber, which allows scintillatorreplacement without breaking the system vacuum. FIG. 13A is across-sectional view (similar to FIG. 12A) showing 4 of the 6 arms asseen from the front. FIG. 13B is a cross-sectional perspective view thatshows the approximately 45° scintillator-frame angle with respect to thebeam, camera and PMT. FIG. 13C is a perspective view of the closed6-way-cross load-lock vacuum chamber.

FIGS. 9-13 are based on “off-the-shelf” 6-way-cross configurations thathave been modified such that the inner flanges associated with the twovertical tubes/arms as seen in FIGS. 9-13 are reduced or shortened tothe minimum length required to weld each vertical flange to the crossbody. The purpose of this modification is to position the cameras and/orPMTs as close as possible to the beamline axis/cross-center to improvethe photon collection efficiency. However for some applications it ismore important that the total length of the cross from theentrance-to-exit flange be minimized, and for such cases the twohorizontal tubes/arms along the beam axis are shortened to the minimumstub size required to weld each flange to the cross body. For example,in the case of a beam monitor based on a 4″ O.D. tube system with 6″diameter CF-flanges, the total length of the beam monitor includingflanges from end-to-end can be reduced to under 6″. FIGS. 27A-Billustrate a system 2700 that includes both a side view (FIG. 27A) andperspective view (FIG. 27B) of the open central structure of the abovereduced/shortened 4″ O.D. tube, 6-way-cross with 6″ diameter CF-flangesmodified such that the total beam entrance-to-exit length is ≤5.9″ inaccordance to vacuum chamber embodiments. The 4″ tubes that connect tothe top and bottom 6″ CF-flanges that connect to the viewport windows,and subsequently to the full nipples that accommodate the camera andPMT, are also shortened such that the total end-to-end length for thesetwo flanges is ≤7.9″ in accordance to embodiments. Depending upon theapplication requirements, the described priority can always be changedsuch that if the 4″ O.D. tube, 6-way-cross embodiment shown in FIGS.27A-B is rotated by 90 degrees, then the end-to-end length for the two6″ CF-flanges to the camera and PMT viewport windows would be 5.9″ whilethe minimum total beam entrance-to-exit length would be 7.9″ inaccordance to embodiments.

FIGS. 14A-D illustrate a system 1400 that includes a two camera, twomirror, full-size single scintillator/window module beam monitor in aslim light-tight enclosure in accordance with embodiments. In oneembodiment a “slim” light-tight enclosure is 5″ thick or less; however,depending upon the patient size requirements, scintillator dimensions,and image spatial and positional resolution specifications, thethickness can typically vary over a range from about 3″ to 7″. FIG. 14Ais a perspective view of the components of a “drop-in”window/scintillator frame module. FIG. 14B shows how thewindow/scintillator frame module drops into one of the cover platepockets. FIG. 14C is a perspective drawing of the two camera, singlescintillator beam monitor enclosure with the top cover plate removed andpositioned above the main structure. FIG. 14D is a cross-sectional viewof the light-tight enclosure with drop-in ultra-thin window 1422 andwindow/scintillator 1460 modules, showing the folded optical design ofcamera, mirror and scintillator, and minimum scintillator field-of-viewby camera-lens system on right side (i.e., within dotted line cone).Also shown in FIGS. 14C and 14D are a UV-LED source and UV-photodiodefor internal calibration.

FIGS. 15A-C illustrate a system 1500 that includes a one camera, onemirror, half-size rectangular single scintillator beam monitor in a slimlight-tight enclosure version of the embodiments shown in FIGS. 14C-D inaccordance with embodiments. FIG. 15A is a perspective view assemblydrawing showing the camera 1540, mirror 1530, ultra-thin window 1522,window/scintillator module 1560, UV-LED source 1550, UV-photodiode 1552,and the box construction with window cover plate 1520 andwindow/scintillator cover plate 1570 based on an internal framestructure. The actual enclosure shape and construction can vary and doesnot have to be rectangular (e.g. can be cylindrical). FIG. 15B is across-sectional view of the light-tight enclosure showing all of thebasic described components. FIG. 15C is a perspective view of theenclosed system.

FIGS. 16A-C illustrate a system 1600 that includes a three cameraversion of the embodiments shown in FIGS. 15A-C in accordance withembodiments. The additional two side cameras do not have to be identicalto the single top camera and can be selected for improvedlight-sensitivity, faster frame rates, and/or higher pixel resolution.FIG. 16A is a perspective view assembly drawing showing the threecameras 1640, 1644 and 1646, associated mirrors 1630, 1634 and 1636,ultra-thin window 1622, and window/scintillator module 1660, based on aninternal frame structure. The actual enclosure shape and constructioncan vary and does not have to be rectangular (e.g. can be cylindrical).FIG. 16B is a cross-sectional view of the light-tight enclosure showingall of the basic described components. FIG. 16C is a perspective view ofthe enclosed system.

FIGS. 17A-B illustrate a system 1700 that includes a four camera versionof the embodiments shown in FIGS. 14A-D for the full-size singlescintillator-frame beam monitor with folded-optics in accordance withembodiments. The two additional cameras allow the field-of-view of eachcamera to be appropriately reduced to a scintillator quadrant, resultingmost likely in selection of a different camera or different lens than inFIG. 14 for improved light-sensitivity, faster frame rates, and/orhigher pixel resolution. FIG. 17A is a perspective view assembly drawingshowing the four cameras 1740, 1741, 1742 and 1743, associated mirrors1730, 1731, 1732 and 1733, ultra-thin window 1722, UV-LED sources 1750and 1751, associated UV-photodiodes 1752 and 1753, andwindow/scintillator module 1760, based on an internal frame structure.The actual enclosure shape and construction can vary and does not haveto be rectangular (e.g. can be cylindrical). FIG. 17B is across-sectional view of the light-tight enclosure showing all of thebasic described components.

FIGS. 18A-B illustrate a system 1800 that includes a four camera,full-size double window/scintillator module beam monitor in alight-tight slim enclosure in accordance with embodiments. Thisembodiment is a double scintillator version of that shown in FIGS. 14A-Dand incorporates both a front and back cover plate pocket design for thetwo “drop-in” window/scintillator frame modules. FIG. 18A is aperspective view assembly drawing showing the four cameras 1840, 1842,1844 and 1846, with their associated mirrors including mirror 1836coupled to camera 1846, aimed at the two window/scintillator modules1860 and 1862. Cameras 1840 and 1842 through their respective mirrorsare aimed at the bottom scintillator/window module 1860, whereas cameras1844 and 1846 through their respective mirrors are aimed at the topscintillator/window module 1862. FIG. 18B is a cross-sectional view ofthe light-tight enclosure and like FIG. 18A shows two cameras with theirrespective folded-optics mirrors aimed at each scintillator.

FIGS. 19A-B illustrate a system 1900 that includes an eight camera,full-size double window/scintillator module beam monitor in alight-tight slim enclosure in accordance with embodiments. FIG. 19A issimilar to FIG. 18A, but the number of cameras has been doubled, similarto FIGS. 17A-B compared to FIGS. 14A-D. Cameras 1940, 1941, 1942 and1943, though their respective fold-optic mirrors, are each aimed at onequadrant of scintillator/window module 1960. Similarly, cameras 1944,1945, 1946 and 1947, though their respective fold-optic mirrors, areeach aimed at one quadrant of scintillator/window module 1962. Mirrors1930 and 1931 for example are coupled to cameras 1940 and 1941. FIG. 19Bis a cross-sectional view of the light-tight enclosure and like FIG. 19Ashows four cameras with their respective folded-optics mirrors aimed ateach scintillator.

FIGS. 20A-C illustrate a system 2000 that includes a four camera, singlescintillator beam monitor employing a rolled scintillator spoolconfiguration in accordance with embodiments, and is similar to the twocamera version shown in FIGS. 8A-C. FIG. 20A is a perspective view, FIG.20B is a top view, and FIG. 20C is a Section A-A view. FIGS. 20A and 20Bshow cameras 2040, 2014, 2042 and 2043, and their associatedfolded-mirrors such as 2030 and 2031. The dotted arrows in FIGS. 20A-Cshow the direction of film movement from the feed roll 2070 to thetake-up roll 2072. In this embodiment, film 2060 would be pulled acrossan active window area 2012 onto a suitable take-up spool 2072, andadvanced by a stepper motor 2080 that rotates the take-up spool spindleas required. An ultra-thin dark colored or black exit window 2014, suchas 15 μm to 25 μm thick black aluminum foil, is shown FIG. 20C, whiletwo UV-LED sources 2050 and 2051, and UV-photodiodes 2052 and 2053 areshown in FIG. 20A.

FIGS. 21A-B illustrate a system 2100 as perspective (FIG. 21A) andcross-sectional (FIG. 21B) views of a two camera 2140, full-size singlescintillator-frame beam monitor in a light-tight box enclosure somewhatsimilar to that shown in FIGS. 14C-D, but using smaller size cameras(e.g., ˜1″×1″×1″) and not employing a folded optical systemconfiguration with a mirror for each camera in accordance withembodiments. Each camera is thus aimed directly at the bottomscintillator plate 2130 resulting in the entire box enclosure beingabout 5 cm thicker than shown in FIGS. 14C-D. By removing the top coverplate and window 2110, and possibly even the side panels, the twocameras can be inserted just behind the exit nozzle or collimator (i.e.,upstream) or alternately described as straddling behind the nozzle orcollimator, and therefore integrated directly into the nozzle orcollimator enclosure with the scintillator/window 2130 module insertedin the pocket of the exit cover plate 2120 located in front (i.e.downstream) of where the beam exits the nozzle or collimator. FIGS.21A-B still incorporate one or two or more UV-LEDs and UV-photodiodes asfound in all of the other beam monitors embodiments.

FIGS. 22A-C illustrate a system 2200 that is a four camera version ofFIGS. 21A-B in accordance with embodiments. By removing the top coverplate and window as shown in FIGS. 22A-B, and possibly even the sidepanels, the four cameras 2240 can be inserted just behind the exitnozzle or collimator (i.e., upstream) or alternately described asstraddling behind the nozzle or collimator, and therefore integrateddirectly into the nozzle or collimator enclosure with thescintillator/window 2230 module inserted in the pocket of the exit coverplate located in front (i.e. downstream) of where the beam exits thenozzle or collimator. FIGS. 22A-C still incorporate one or two or moreUV-LEDs and UV-photodiodes as found in all of the other beam monitorsembodiments.

In connection with the film rolls used in some embodiments, much longerrolls of the thickness and width disclosed above have been used fordecades in aerial photography and advanced by motor drives at highspeed—e.g., Kodak Aerial Ektacolor Print Film (SO-149) which with itscolor emulsion and gel backing has a total thickness of 213 μm. It isnoted that standard 35 mm and 70 mm wide, motion picture film istypically advanced at 24 fps for “normal” motion but faster for slowmotion, and some 70 mm IMAX films have been run at 48 fps (i.e., 200meters/minute). If, for example, the BoPEN film were advanced 5 cm on abiweekly basis to shift the most likely rad-damaged scintillator centerarea (i.e., isocenter region) midway to the side, then the previouslydescribed 20-25 meter film length could last approximately 16 years. Ifthe same BoPEN film were advanced 10 or 20 cm biweekly, then a singleroll would last either 8 or 4 years respectively before requiringreplacement.

Aerial films were previously made in four standard widths, 35 mm, 70 mm,126 mm and 240 mm. These widths are the edge-to-edge dimensions andinclude sprockets on both sides, so for example the maximum image widthon the 70 mm film is ˜58 mm, and on the 240 mm is 228 mm. The thinnestKodak aerial film Estar “Ultra-Thin” Base made was 30 μm (i.e., 0.0012″)but was still strong enough to hold sprocket holes without tearing.However the standard Kodak Estar Ultra-Thin Base was 38 μm (i.e.,0.0015″), while the standard Kodak Estar Thick Base was 178 μm (i.e.,0.0070″). Film roll lengths for the Thick Estar Bases went from 100 to800 feet, whereas film roll lengths of up to 2000 feet were standard forthe other thinner Estar base films. A detailed thickness study by Kodakfor their standard 240 mm wide Estar Base in a standard 30 meter lengthfilm roll yielded that “the thickness variation across essentially theentire roll length had a standard deviation of less than 1.85 μm”.However, within the 23 cm×23 cm aerial format picture area (i.e., 9″×9″)the standard thickness deviation was 1.0 μm. For Kodak 70 mm wide films,the spool core diameter was 31132″ for film roll lengths up to 200 feetfor the Estar Thin Base (64 μm), 150 feet for the standard Estar Base(102 μm), and 100 feet for the Estar Thick Base (i.e. 178 μm withoutemulsion and 184 μm thickness for B/W emulsions and 213 μm for theirthickest color film), For longer rolls of 70 mm wide film, and for alllengths of 126 mm and 240 mm width film rolls, a spool core diameter of2.125″ was used for all Estar film base thicknesses, Thus the suggestedspool core diameter of 2.5″ disclosed above, and film length of 20-25meters, are conservative given the standard specifications used foraerial films, as is the film thickness uniformity across the activearea.

For the multi-arm cross, roll film embodiments, the 25 μm thick BoPENshould be ideal, especially considering that the BoPEN film is strongerthan the Estar Base film (i.e., BoPET) used by Kodak, and the sprocketfilm holes that can tear in rapid advance photographic film systems arenot required for the much slower advancing roll-to-roll embodimentsdescribed herein. In addition, the 12 μm thick BoPEN is also apotentially viable thickness for the roll-to-roll scintillator filmdesigns such as the highly transmissive beamline vacuum cross monitorsshown in FIGS. 9 and 10 . In terms of the mechanical viability of suchultra-thin film rolls, it is noted that 12 μm thick linear low-densitypolyethylene (“LLDPE”) is available on a 3″ core in 18″ wide rolls of1500 ft length (i.e., sold as a 47-gauge thick, polyethylene hybridfilm), and even thinner 7 μm LLDPE film is available as 28-gauge filmalso on a 3″ core in 1500 ft length rolls. With regard to film strength,BoPEN is much stronger than LLDPE, having at least three times thetensile strength. As such, BoPEN rolls/coils are available in ultra-thinfilms down to 1.3 μm thickness in 12″ and wider size rolls, whereas 12μm thick BoPEN film is available in 40″ wide rolls of 9800 ft length.

For embodiments that do not require roll-to-roll film advance systems, avariety of simpler yet more versatile transmissive beam monitorembodiments have been designed for fast exchange of differentscintillator materials optimized for a wide variety of ionizingparticles and energies including photons and neutrons in a wide range offilm and sheet thicknesses (e.g., from ˜1 μm to ≥1 mm). For thosemonitors designed for beamline applications, both single-frame anddouble-frame, multi-arm cross structures are disclosed in which thescintillator is mounted to a stiff frame in contact with a push-pullmechanism as shown for three different 6-way-cross embodiments in FIGS.11A-D, and 12A-C, and 13A-C below. If only one camera is required and noPMT, then a less expensive 5-way-cross can be employed, and dependingupon the frame and arm (or nipple) length, the scintillator can bepulled out of the beam path entirely and pushed into the beam path onlywhen beam monitoring is required (e.g., as shown in FIG. 12B). Anotheradvantage of mounting the scintillator film to a rigid frame, ascompared to a roll-to-roll system, is that thick scintillators (e.g.,≥0.5 mm) cannot be rolled onto a small diameter spool, while thethinnest scintillator films of only a few microns cannot be reliablyadvanced across the beam axis transit area without risk of damage whenpulling it from the feed spool 1030 onto the take-up spool 1024 as inFIG. 10A. As disclosed, 3, 6, 12 and 191 μm thick BoPEN films haveunexpected characteristics of radiation hardness and fast recovery (seeFIG. 3 ). Other embodiments can use 1.3 μm BoPEN films or 250 μm thickBoPEN films for several different applications.

All of the embodiments disclosed herein with associated figures/drawingsincorporate the previously described system/hardware required forinternal calibration and beam image analysis. The calibration system andits operation can be initiated either manually or automatically (e.g.,on a pre-programmed schedule) and is based on activating an internalUV-LED source or sources to illuminate the scintillator film for a shorttime (e.g., seconds) and capturing images of the fluorescence intensitypattern and comparing them to previous images by means of an appropriatecomputer system to detect any changes in the system response, includingchanges in the scintillator fluorescence or camera sensor such as mightbe caused by radiation damage, etc. In order to monitor the stability ofthe UV-source, each UV-LED is itself monitored by a dedicated proximityUV-photosensor such as a photodiode to correct for any source intensitychange or drift over time. The computer system in one embodiment is adedicated, low-latency, fast-PC (personal computer) or workstation,etc., having a processor that executes instructions. In otherembodiments, the computer system is a customized FPGA based PCB (printedcircuit board) or frame grabber, although more likely a frame grabberconnected to a computer. For some systems the FPGA could be partially orfully embedded in the camera(s). The computer system besides performinginternal calibration checks, is also programmed to perform imageanalysis in real-time of the beam as it irradiates the scintillator soas to monitor and analyze in two-dimensions (“2D”) the beam position andbeam shape, beam movement, the beam intensity profile including tail,beam fluence and external dosimetry, and beam angular divergence in thecase of the beam monitor configuration incorporating two or morescintillators in the beam path and separated by an appropriate distance.In addition, because all of the embodiments incorporate one or moremachine vision cameras oriented at an angle to the scintillator plane,all of the camera images will incur perspective/tilt distortion (i.e.,keystoning), while the camera lenses, especially due to their closeworking distance, will exhibit some amount of optical distortion as wellas vignetting, and the camera sensors themselves can never be perfectlyuniform in terms of each pixel having exactly the same response. All ofthese system hardware related non-uniformities can be corrected bycalibration of the integrated system and frequently checking thiscalibration by taking repeated images of the system response to theUV-source illuminated scintillator and automatically adjusting thecalibration as needed by the computer system.

In order to minimize maintenance and down time, and to further optimizethe design, fast scintillator replacement is required in embodiments.This is achieved in all of the embodiments shown in FIGS. 14-19 and21-22 by the design of a thin (e.g., 2 mm to 3 mm thick), replaceablelarge window/scintillator frame module assembly such as 1460 in FIG. 14Athat can be easily accessed and dropped from the outside into a smallpocket (˜2-3 mm deep) in the front and/or back enclosure cover plate(s)1414, and secured from the outside with a thin 1-2 mm thick retainingframe 1410 as shown in FIG. 14B. The window/scintillator module assembly1460 consists of ultra-thin window 1402, such as 15 μm to 25 μm thickblack aluminum foil, and a scintillator film or sheet 1406, with bothcomponents attached or glued to opposite sides of a thin frame 1404,Replacement of the ultra-thin window/scintillator module using thedesign in FIGS. 14A-D should take only a few minutes. If only onescintillator/window module 1460 is employed, then an ultra-thin windowby itself such as 1402 is glued to the frame 1404 without adding thebottom scintillator plate. The window module itself, without ascintillator component, is shown as 1422 in FIGS. 14C-D and fits intothe pocket of cover plate 1420 and held in place by a retaining frame(e.g., 1410 in FIG. 14B) as shown in FIG. 14C. FIGS. 14C-D show one suchembodiment based on a 2 camera, 1 scintillator arrangement, with bothcameras 1440 and 1442 indirectly aimed at the back scintillator 1406 inthe back window/scintillator module 1460 through their respectivefolded-optics mirrors 1430 and 1432. Also shown are UV-LEDs 1450 andUV-photodiodes 1452 in FIGS. 14C-D.

Embodiments include a number of different light-tight enclosure beammonitors incorporating one or two scintillators and from one (1) totwelve (12) or more cameras, depending upon the desired beamspatial/positional resolution and the required scintillator active areasize which for EBRT applications can typically extend up to about 40cm×40 cm. In general, for a 20 cm×20 cm scintillator, the intrinsic 2Dposition resolution should be on the order of ˜0.03 to 0.2 mm, dependingupon the required UFT beam monitor specifications. However, no matterhow many cameras are employed, such as 1, 2, 3, 4, 6, 8, 10, 12 or more(see FIGS. 8 and 14-22), the software required for stitching multiplecamera images together is commercially available for scientific,industrial, medical, consumer applications, etc. For example, a numberof smartphones now employ multi-camera systems, such as the SamsungGalaxy S10 and S10+, which use 3 cameras to stitch together high qualityimages with minimal distortion that can cover the full range fromultra-wide angle to telephoto. The above disclosed platform can performthe equivalent of stitching together multiple images as they stream infrom multiple machine vision cameras in order to track and analyze themoving particle beam or photon beam as it travels both horizontally andvertically across the scintillator surface. For such streaming imagesthe software in embodiments is mostly FPGA based, on a multi-cameraframe grabber based system that can provide calibration and correctionsfor optical distortions and equipment/system non-uniformity.

Depending upon the application requirements in terms of: image/pixelresolution, low-light sensitivity, pixel bit depth (i.e., gray scale),exposure time (i.e., shutter speed), frame rate, and image processingspeed including system latency, camera images can be streamed live,processed and analyzed in real-time at rates potentially as fast as25-100 μs per image (i.e., 10,000-40,000 fps) depending upon the systemhardware, firmware and software, including the choice of camerainterface. For example, machine vision cameras operating at over 30,000fps, corresponding to a timing resolution of ˜33 μs, can still providesub-mm image resolution for embodiments such as the above multi-camera,20 cm×20 cm, or even 40 cm×40 cm, scintillator EBRT beam monitors at acost of about $5K to $8K per camera is single unit quantities. Thelarger size 40 cm×40 cm scintillator beam monitoring systems inaccordance to embodiments employ 4 or more cameras, and are configuredif desired with two different types of cameras—for example in asingle-scintillator 6-camera configuration there could be fourrelatively inexpensive high picture resolution, low frame rate (fps)cameras, plus two of the more expensive high fps cameras; othercombinations are also possible such as 4 slow and 4 fast cameras, or 4low sensitivity and 4 high sensitivity cameras in a 8-camera system. Infact, low cost, high spatial resolution, low sensitivity, low fpscameras could even be paired side-by-side with ultra-fast, highsensitivity, ultra-compact PMTs (e.g., Hamamatsu H11934 series withdimensions of 30 mm×30 mm×32 mm) with camera lenses coupled to each PMTthereby viewing the same scintillator area as the camera. The PMTs wouldprovide the low-light sensitivity and dose rate information withultra-fast ns and sub-ns response capability (e.g., 10 ns is equivalentto 100,000,000 fps). For applications requiring frame rates of1,000-2,000 fps or slower, smaller size machine vision cameras can beprocured for ≤$1K (see below).

FIGS. 23A-B illustrate camera images through a vacuum chamber window ofa ˜3.6 mm diameter proton beam, moving at 80 mm/ms, irradiating a 191 μmthick BoPEN scintillator, with a 10 μs exposure in accordance toembodiments. The camera used is a Basler daA1280-54 um with a 25 mm FL,f/1.4 lens, at a working distance of ˜350 mm, with a pixel field-of-viewof 48 μm×48 μm. FIG. 23A constitutes an image of the camera's fullfield-of-view.

In FIGS. 23A-B, the proton beam energy was 5.4 MeV at a 10 nA beamcurrent. FIG. 23B is an enlarged and cropped image with the backgrounddigitally removed of the beam spot area in FIG. 23A, showing the pixelresolution detail including the intensity distribution and beam shapeand dimensions which covers an irregularly shaped elliptical area of˜60×100 pixels. The beam horizontal “smear” during the 10 μs exposuredue to the 80 mm/ms movement is only ˜0.8 mm, or about a 22% elongation.

FIG. 24 illustrates a 1 ms exposure of a captured image using the samecamera/lens as in FIG. 23 , but of a ˜2 mm diameter proton beamirradiating an ultra-thin 12.2 μm BoPEN film while moving back and forthin a rastered zig zag pattern at 40 mm/ms in accordance to embodiments.As with FIGS. 23A-B, the proton beam energy is 5.4 MeV at a 10 nA beamcurrent, but at a lens working distance of ˜390 mm, corresponding to asomewhat larger 55 μm×55 μm field-of-view pixel resolution. Similarimages have been captured on BoPEN films as thin as 3.0 μm, with plansto irradiate a 1.3 μm thick BoPEN film in the near future.

One embodiment uses Universal Serial Bus (“USB”) as the systeminterface, hardware and processing software, which is capable ofprocessing and analyzing images at rates up to about 1,000-2,000 fps(i.e., 1.0 ms to 0.5 ms). For higher performance, embodiments use anumber of faster camera interfaces for interfacing with high-speed FPGAbased frame grabber hardware, firmware and software, to process andanalyze the streaming images at much higher speeds, including CoaXPress2.0 (CPX-12), GigE (10 Gigabit Ethernet), Camera Link HS, etc.

Referring again to FIGS. 11A-D, both cross-sectional and perspectiveviews of a single scintillator-frame beam monitor are shown. FIG. 11Ashows 4 of the 6 arms of a modified CF-flange 6-way-cross vacuum chamberconfiguration, although any type of flange system can be used (e.g.,ConFlat, KF/QF, ISO-K, ISO-F, ASA, Wire-Seal, etc.). The two arms notshown in FIG. 11A are perpendicular to the plane of the drawing wherethe beam enters 1101 the cross center as seen in FIG. 11B. Either orboth of these two arms can incorporate an optional gate valve attachedto one or both flanges for vacuum isolation. FIG. 11B shows one suchgate valve 1110 attached to the exit arm flange. As the integratedexposure of the scintillator to the ionizing beam accumulates over time,so does the radiation dose which would typically be concentrated in ornear the beam pipe center. Therefore, at such time that the scintillatorradiation damage becomes significant, the scintillator-frame unit 1140is nudged or pushed by shaft 1172 an appropriate distance (e.g., ˜1 cm,or more) on its track 1145 in FIG. 11D towards the opposite side (i.e.,the right side in FIGS. 11A-D) to bring unexposed or minimally exposedscintillator film into the central beam path region. This linearshift/movement can be accomplished either manually, or controlledpneumatically, or by a stepper motor as indicated by the linearpositioner 1170 shown on the left side in FIG. 11A.

FIG. 11A shows the camera 1104 and camera lens 1106 in the top nipple,along with the UV-LED/UV-photodiode assembly combination 1180, and aconical reducer nipple 1190 to the vacuum-exhaust/air-bleed line (notshown). FIG. 11D shows a close-up of the two small UV-LEDs 1186 andUV-photodiodes 1182 positioned on opposite sides of the camera lens. ThePMT 1160 in the bottom nipple is shown most clearly in FIG. 11C, whilethe two condensing lenses 1150 and 1152 on either side of the viewportwindow 1156 in the bottom nipple are best seen in FIG. 11D. FIG. 11Dprovides a close-up magnified view of the 6-way-cross center area inwhich the two viewport windows 1155 and 1156, UV-LEDs, UV-photodiodes,two scintillator-frame tracks, and the two condensing lenses are mosteasily seen.

Most of the embodiments disclosed herein include at least one UVillumination source, with at least one UV photosensor to monitor thestability of each UV source. The UV source employed in some embodimentsfor the BoPEN scintillator is a UV-LED with peak emission at ˜280 nm,where the BoPEN scintillator film essentially absorbs at least 99% ofthe source photons at the film surface within a ˜0.1 μm thick layer. TheUV photosensor used to monitor the UV-LED in embodiments is aUV-photodiode. If needed, the UV source and/or UV photosensor can becoupled to a suitable UV bandpass or UV shortpass filter. When therad-damage in any particular area starts to become significant, thescintillator-frame is pushed slightly towards the far side until suchtime as the frame has been pushed completely to the far side as shown inFIGS. 11A and 11D. Once the scintillator has been fully radiationdamaged along its useable length, the scintillator-frame is then pulledback to its initial position and the scintillator-frame replaced.Replacement requires breaking vacuum in the 6-way-cross chamber, butbecause of the excellent BoPEN rad-hardness (see Table 1 above) it mightbe possible to schedule such replacement during preplanned downtimeperiods allocated for general maintenance.

If the scintillator 6-way-cross chamber includes both entrance and exitgate valves, then breaking vacuum is limited to the small chamber volumewith no impact on the rest of the beamline and so scintillator-framereplacement can be done whenever convenient and should only take aboutan hour or so including ambient pressurization and re-evacuation. Otherfeatures of consequence are the machine vision camera in the top arm,the PMT in the bottom arm, the push-pull linear positioner on the leftside, and the reducer nipple on the right side which is connected to asmall vacuum pump system (not shown) with a bleed valve for chamberpressurization followed by re-evacuation. Also not shown are thedescribed beam entrance gate valve, although the exit gate valve iseasily seen in FIGS. 11B and 11C and so an entrance gate would look thesame when attached to the entrance flange in FIG. 11B. Both the cameraand PMT in their respective nipples are kept in an air atmosphere atambient pressure. This is achieved on the camera side by having a UVtransparent viewport window 1155 inserted between the cross flange andthe camera nipple. The reason for a UV window is because the UV-LED inthis embodiment is located on the side of the camera lens. If the camerapower consumption is large enough to cause significant heating, then thenipple back flange can be left open or vented to facilitate air coolingby either natural or forced convection as long as the front of thecamera or lens barrel is appropriately light shielded behind the UV-LEDand UV-photodiode. The same viewport window arrangement is used on thePMT side, but for the BoPEN scintillator or other scintillators withshorter decay times (e.g., EJ-200, EJ-204, EJ-212, EJ-228, EJ-262, etc.from Eljen Technology) with emission peaks in the violet-blue-cyanregion, the viewport window 1156 can be glass.

To maximize the PMT light collection efficiency a set of highlyefficient, high transmission glass (e.g., Schott B270) asphericcondensing lenses are employed with an f/number that can be less than1.0 (e.g., between f/0.6 to f/0.9). For maximum efficiency, the firstcondensing lens 1150 is located inside the cross vacuum chamber justbelow the scintillator/frame, while the second lens 1152 is located justbelow the glass viewport window 1156 and in front of the PMT at ambientpressure as shown in FIG. 11D. Both lenses can be anti-reflection coatedfor maximum light transmission and the second lens located in front ofthe PMT can further reduce reflection loss by optically coupling it to amatching refractive index plastic or glass light guide (e.g., cylinder)thereby eliminating the air gap completely. The PMTs should be selectedfor minimum jitter (e.g., ≤0.3 ns), maximum quantum efficiency (e.g.,≥22%), and most importantly for maximum gain (e.g. >1×10⁶). Besideshaving a short decay time, the scintillator should have a high lightyield and if capable of total internal reflection (TIR) could have areflective coating deposited on the non-collecting surface, or surfaceroughened to eliminate TIR on the light collect surface, or for optimumTOF performance could employ two matching PMTs with two sets ofcondensing lenses in the 6-way-cross (i.e., replacing the camera with asecond PMT).

The embodiment shown in FIGS. 12A-C is similar to that in FIGS. 11A-D,but with the addition of two horizontal full-nipples 1290 and 1292 toaccommodate a dual scintillator-frame configuration. Similarly theembodiment in FIGS. 13A-C is quite similar to that in FIGS. 12A-C, butwith the important addition of two vertical gate valves 1310 and 1311that effectively transform the embodiment in FIG. 12 into the load-lockvacuum chamber of FIG. 13 . FIGS. 12A-B show 4 of the 6 arms of thecustomized 6-way-cross vacuum chamber; the two arms not shown areperpendicular to the plane of the drawing where the beam enters andexits the cross center. FIG. 12C is a perspective view showing all 6sides/arms, including the two perpendicular arms where the beam enters1201 and exits 1202 and which can incorporate one or two optional gatevalves such as 1310 and 1311 as shown in FIGS. 13A-C and previouslydiscussed for FIG. 11 . The dual scintillator-frame embodiments employeither a straight track 1245 or a segmented track 1345, as shownrespectively in FIGS. 12A and 13A that goes through all three chambersections on which the scintillator-frames can be pushed or pulled. Iftwo identical scintillators are employed, the maximum time beforescintillator replacement can be essentially doubled. The dualscintillators 1240 and 1241 in their frames as illustrated in FIGS.12A-B also allow two different scintillator materials to be employed,each selected for a different purpose. For example, one scintillatormight be selected for minimum film thickness and maximum beamtransmission (e.g., BoPEN), with the other selected for minimum decaytime and rise time to provide the fastest possible timing when coupledto an efficient light-collection system such as the condenser lenssystem shown in FIGS. 12A-B, which can be seen more clearly in FIG. 11Das lens elements 1150 and 1152, and a fast PMT 1060, 1160 & 1260 inFIGS. 10A, 11C and 12B respectively for sub-ns TOF (time-of-flight)measurements. With embodiments, timing resolutions of ≤0.1 ns areachievable for highly ionized, high-Z (i.e., atomic number) beams usingthe 6-way-cross beam monitors shown in FIGS. 10A, 11A-D and 12A-B.

As discussed above, for the embodiment shown in FIGS. 12A-C, the twoscintillators mounted in their respective frames can either be identicalor the first scintillator-frame combination 1240 might be selected forfast timing (e.g., BC-400 from Saint-Gobain) and the second being athinner scintillator 1241 of different composition, such as BoPEN,selected for maximum beam transmissivity with minimal beam scatteringand energy loss (i.e., from an incident photon or particle beam such asprotons, ions, electrons, neutrons, etc.). The scintillator-frame 1241in its initial start position is shown in FIG. 12A before being nudgedor pulled in small steps towards the opposite (i.e. right) side as inFIG. 12B to bring unexposed or minimally exposed scintillator film intothe central beam path region. Such linear movement can be accomplishedeither manually with linear push-pull positioners 1220 and 1230 in FIG.12A, and 1320 and 1330 in FIG. 13A, or controlled pneumatically or by astepper motor.

As the integrated exposure of the scintillator to the ionizing beamaccumulates over time, so does the radiation dose which would typicallybe concentrated in or near the beamline cross center 1250 shown in FIG.12B. The two horizontal length nipples 1290 and 1292 hold the twoscintillator-frames 1240 and 1241 in FIG. 12B with scintillator-framepush-pull linear positioners 1220 and 1230 attached to their respectivenipple and scintillator-frame that push or pull the two scintillatorframes on their tracks from the left side across the beam center area1250. When fully “used up” (i.e. radiation damaged) the centerscintillator-frame is pulled from the right into the right side nipplechamber 1292 in FIG. 12A (or 1392 in FIG. 13A) for removal, while theleft scintillator-frame 1340 in the left side nipple 1390 in FIG. 13Acan be pushed into the center of the 6-way-cross where the beam entersthrough flange 1301 in FIG. 13C. The top vertical nipple contains thecamera 1004, 1104, 1204, 1304 in FIGS. 10-13 respectively, and cameralens 1006 or 1106, while the bottom vertical nipple contains the PMT1060, 1160, 1260 or 1360 (or SSPM). The two vertical nipples containingthe camera and PMT are at ambient pressure and isolated from the vacuumby their hermetically-sealed windows—e.g. 1155 and 1156 shown in FIG.11D. The scintillators are pushed-pulled along a three sectionchannel/rail or track 1345 in FIGS. 13A and 13B with two breaks oropen-segments of ˜2 cm each through which the two gate valves 1310 and1311 can close. The scintillator-frames 1340 and 1341 can each beremoved without breaking vacuum by closing a gate valve. With the gatevalves closed, each scintillator nipple section can be individuallypressurized for scintillator replacement and then re-evacuated using asmall pump through the two nipple tee sections 1391 and 1393.

The embodiment shown in FIG. 12 does not have any gate valves to isolateeach nipple during scintillator replacement, so “nipple” 1290 isactually a reducer tee with reducer flange 1291 for connection to anexternal pressurization line and optional vacuum line to minimizedowntime during scintillator replacement. This arrangement is similar infunction to the conical reducer nipples 1090 and 1190 shown in FIGS. 10Aand 11A for attachment to an external pressurization/vacuum-exhaustline. Although not easily seen in FIG. 12 or 13 , for internalcalibration purposes the described embodiments include UV-photodiodes1082 and 1084, as shown on each side of the camera lens 1006 in FIGS.10A and 10C, to monitor the output of each UV-LED 1086 and 1088 in orderto correct for changes in the UV-LED output luminosity. This internalUV-LED/UV-photodiode calibration system 1080 in FIG. 10A, also shown as1180 in FIG. 11A, and 1182 and 1186 in FIG. 11D, can also be used tomonitor and correct for any changes with time or temperature of thecamera sensor output.

Depending upon the specific application and beamline monitoringrequirements, a number of variations of the 6-way-cross structuresdescribed above and in FIGS. 9-13 are available. For example, if a PMTis not required, then a 5-way-cross can be used, but if spatialresolution, sensitivity and accuracy are paramount, then the 6-way-crosscould be used with two cameras—i.e. the second camera replacing the PMTas shown in FIG. 9A. Alternatively, if the beamline monitor is to beoptimized for time-of-flight (“TOF”) measurements with the highesttiming resolution and accuracy required, then two closely-matched PMTswith two sets of condensing lenses can be employed, and the cameraeliminated as discussed previously. For other applications only a3-way-tee or 3-way-wye might be required, or a 4-way-cross could beutilized.

Not all beamline monitoring systems need to be integrated into a vacuumbeam pipe environment, including segments of electron and neutron beamdelivery systems. Such systems, however, can still utilize the variousmulti-arm-cross embodiments disclosed herein. For monitoring the beam inair, the crosses do not have to be evacuated but can simply be madelight-tight by adding a thin foil or dark/black polymer film window, orsome polymer-foil combination thereof, to the entrance and exit flanges.For enhanced scintillator recovery, the air atmosphere can be replacedby any gaseous atmosphere including oxygen or oxygen enhanced mixtures,or pure nitrogen or argon or any other type of specified atmosphere.

All of the embodiments with cameras include the camera or camerasviewing the scintillator at various angles of incidence or reflection,the latter indirectly via a folded-optics mirror system. Parameteroptimization determines the most appropriate camera lens angle ofincidence with respect to the normal to the scintillator plane (i.e.surface) or mirror for each application. For most of the embodimentsdisclosed here, the camera lens viewing angle with respect to thescintillator will typically fall within the range of 25-65°, with anaverage value of ˜45°. For the camera images captured in FIGS. 6, 23 and24 , the camera angle of incidence with respect to the scintillatornormal typically fell within 10-20°. For the embodiments in FIGS. 8-22 ,the mean camera angle with respect in the scintillator normal, or mirrornormal in the case of FIGS. 8 and 14-20 was typically 40-50° but can beincreased to minimize the enclosure depth or thickness. However, anycamera angle greater than a few degrees will create some angulardistortion of the image, and depending upon the amount of distortion, acircle, for example, can look like or appear as a distorted ellipse. Infact, for a camera to scintillator angle of just 5°, the distortion willstart to be noticeable, and at a 10° angle the distortion willdefinitely be noticeable. Therefore at the 10-20° angles for the imagesin FIGS. 6, 23 and 24 , the discussed ellipsoids might actually becircles but only appear to be ellipsoidal due to this distortion. In thecase of images of a moving or rastering beam, the beam motion willfurther distort the shape of the image in the propagation direction (seeFIGS. 23 and 24). These image distortions can be corrected by software.

FIG. 25 illustrates a four plate light baffle 2500 for air circulationwithin a light-tight enclosure by natural convection in accordance toembodiments. A more efficient light-tight air circulation arrangement bymeans of forced convection can be realized by the addition of one ormore miniature fans.

FIG. 26 is a photograph of a 25×25 cm rectilinear image taken at 45°tilt angle in accordance to embodiments. FIG. 26 shows perspectivedistortion, also known as the keystone effect (e.g., imageforeshortening caused by the angle-of-tilt with respect to the lensorientation).

The angular distortion disclosed above caused by the angle of tilt, asshown in FIG. 26 , is known as a perspective distortion, but also calledtilt distortion, the keystone effect, keystone distortion, or simplykeystoning. A familiar example occurs when taking a picture of a tallbuilding from the ground, with the building looking more and moretrapezoidal the taller it is and the greater the camera angle of tilt.None of the images presented herein have been corrected for thisdistortion, but it is easily corrected in real-time with modern imageediting software. Obviously the greater the angle of camera lens tilt,the greater the distortion, and the greater the difference in imageresolution at the image top edge as compared to the bottom edge. Forexample, in FIG. 8 and FIGS. 14-22 , at an average camera lens viewingangle with respect to the scintillator of ˜60° instead of the 45° anglein FIG. 26 , there will be approximately a factor of two (i.e., 2X)difference in image resolution at the image top edge compared to thebottom edge for a camera focused on the center of a 10 cm×10 cmscintillator quadrant (e.g., FIG. 17 and FIGS. 19-20), with a 10 cmworking distance from the camera lens to the closest point of the imagefield (i.e., top of quadrant). Angles of 60° or even greater arenecessary for achieving the thinnest beam monitor configurationspossible, such as those required by BNCT, disclosed below.

Although the above embodiments have mostly been described and tested interms of their applicability to proton beams and proton beam therapy,these embodiments are applicable to all types of particle beamsincluding those for particle beam therapy (e.g., protons, helium-ions,carbon-ions, electrons, etc.), as well as neutron particle beams. Fastneutrons can still benefit from the described advantages associated withBoPEN scintillator films, but slow to thermal neutrons require boron orlithium or gadolinium doped scintillators, such as boron doped EJ-254,which is of interest for boron neutron capture therapy (“BNCT”) andgadolinium neutron capture therapy (“GdNCT”). Although most of thedisclosed embodiments have referenced the BoPEN scintillator, none ofthe embodiments are scintillator specific, so any scintillator materialcan be employed. The described embodiments are also of interest toparticle research accelerators. The particle beams used for suchresearch include everything from electron and muon beams, to rareisotope and exotic heavy-ion and radioactive ion beams such as highlycharged uranium ions beams (e.g., U-238 with a net charge of +92). Inaddition there are tens of thousands of particle beams used by industryand various versions of these embodiments could find application there.

Embodiments can also be used for external beam radiation therapy(“EBRT”) based on high energy photon beams (e.g., MeV gammas and/orX-rays). Embodiments disclosed herein, such as those in FIGS. 8 and14-22 , have advantages over the known ionization chamber beam monitorsthat find wide application in photon EBRT, with even more advantages forFLASH therapy. These advantages over ionization chambers include up totwo orders-of-magnitude faster beam profile imaging time (e.g., ˜10 μsvs. 1000 μs), at least one order-of-magnitude better intrinsic 2Dposition resolution (e.g., ˜0.03 mm vs. 1 mm), and more than oneorder-of-magnitude higher dose rate capability (e.g., ˜5,000 Gy/s vs.120 Gy/s). Although all of the light-tight ambient pressure beam monitorenclosures shown in FIGS. 8 and 14-22 are rectangular in shape, this isnot a requirement or a limitation, and thus other shaped enclosures canbe employed such as cylindrical shaped beam monitor enclosures. Inaddition, the thickness of the above referenced ionization chambers andthe scintillator based UFT beam monitor can be almost the same,depending upon specifications.

The highest performance cameras with the largest sensor size, bestlow-light sensitivity, highest bit depth (i.e., pixel gray scale range),highest frame rates, most sophisticated embedded FPGA circuitry, andthus the highest data transmission output in terms of MB/s, consume themost power. The maximum power consumption for such cameras could be onthe order of ≥10 watts per camera, although the standby power when thecamera isn't running would likely be much less depending upon thecamera. And for smaller cameras, such as those used for the images inFIGS. 23 and 24 , the average power consumption was only ˜2 watts.Nevertheless, for the case of higher power consumption cameras operatingin a sealed enclosure, heat generation followed by heat build-up couldpotentially be a problem if not adequately addressed.

Several solutions exist to the potential problem of heat build-up,including the use of a series of internal baffled air-vents withstaggered holes to block light leaks, as for example in FIG. 25 , thatwould allow cooling by natural air convection. The total thickness ofsuch vents need not be more than 2-3 cm. If necessary this concept canbe augmented by forced convection if coupled to one or more miniaturefans (e.g., 2-inch to 4-inch blade diameter) for forced-air cooling. Aminimum of two such vented light baffles would be required, preferablyattached to opposite sides of the scintillator box enclosure—i.e., anentrance baffle for air/oxygen in-flow, and exit baffle for air/oxygenout-flow. The FIG. 25 (Side View) drawing uses dashed arrows toillustrate the air flow through the staggered holes of the light bafflevent from entrance 2501 to exit 2502. The purpose of the light baffle isto facilitate continuous circulation and exchange of cool ambient airflow through the scintillator box enclosure, or of cold gas such ascryogenically cooled nitrogen, or of oxygen enriched air, or even pureoxygen circulation through the scintillator box enclosure, whilepreventing or minimizing light leakage. The motivation for oxygencirculation in the scintillator box enclosure is that oxygen diffusioninto the scintillator can potentially minimize scintillator radiationdamage by facilitating partial recovery or repair of scintillator damageby oxygen scavenging of radiation damaging free-radicals created in thescintillator by the incident ionizing radiation beam.

Alternatively the light-tight enclosures can be sealed around the cameralenses, with the camera body protruding out of the light-tightenclosures and thereby venting the camera heat to the external ambientopen-air environment. For the 6-way-cross systems, a custom short nipplecan be made with a light-tight seal (e.g., double O-ring) to the cameralens, thus leaving the camera body protruding outside and beyond thenipple flange to the external atmosphere. There is also the option ofusing active cooling of the camera or silicon image sensor, or evencryogenic cooling, as some cameras are sold with thermoelectric cooledsensors. Finally, each camera and/or sensor could be calibrated fortheir signal response or drift as a function of temperature, and thenthe temperature of the camera or sensor in its enclosure monitored andits signal response automatically corrected by software.

For the detection of neutrons in EBRT applications, the two most obviouslocations for a neutron beam monitoring system might be: (1) immediatelyafter the Li target, but before the moderator, where mostly slowneutrons but perhaps some fast neutrons (e.g. ˜0.8 to 1 MeV) aretypically generated by a ˜2.6 MeV proton beam, and (2) at a locationafter the moderator where the neutron energy is degraded for many boronneutron capture therapy (BNCT) treatment regimens to the epithermalenergy range but more broadly across the range from thermal to slow oreven fast neutrons. If only one neutron beam monitor is to be employed,the most important location would be right after the moderator and infront of the patient. Recent trials in Finland suggest that 1-30 keV“slow” neutrons constitute a practical energy range for BNCT treatment.Essentially all of the beam monitor embodiments disclosed herein shouldwork well for the detection and monitoring of neutrons createdimmediately after the Li target in location (1) above, where the neutronintensity of the BNCT machine is estimated to be on the order of ˜10¹³n/s, corresponding to about 5×10¹³ scintillating photons per second froma 0.2 mm thick BoPEN film. Therefore a much thinner scintillator filmcan to be used to minimize interaction with the beam, and still producea huge amount of scintillating light. For example, a 12 μm thick BoPENfilm scintillator should yield about 3×10¹² scintillating photons persecond. However, for beam monitoring in location (2), the addedmoderator plus energy filtering greatly reduces the number of epithermalneutrons by at least several orders-of-magnitude, which aresignificantly more difficult to detect anyway due to their lower energythan the more energetic “slow” neutrons in location (1). This means thatfor neutron beam monitoring after the moderator, B¹⁰ or another highneutron cross-section isotope (e.g., Li⁶ or Gd) loaded scintillator isrequired to increase the deposited energy in the scintillating host.Such scintillators are available in plastic sheets and can beincorporated in the scintillator-frame embodiments disclosed above andshown in FIGS. 11-22 .

For BNCT head and neck EBRT therapy, the patient's head is typicallypositioned very close to the neutron beam exit nozzle, and therefore thethinnest profile beam monitors are required corresponding to the largestcamera-lens angles with respect to the scintillator normal (e.g.,60°-70°). Modified versions of FIGS. 14-19 with camera angles of ≥60°have been designed for such applications with total beam monitorthicknesses of ˜6 cm to 8 cm (i.e., from entrance to exit window), whichis almost the same thickness as an ionization chamber. These embodiments(not shown) look similar to FIGS. 14-19 , just thinner due to the moresevere average camera-lens angle of ˜60°-70° as compared to the ˜45°angle in FIGS. 14-19 .

For the above disclosed neutron beam monitors, several high neutroncross-section isotope loaded scintillators are available, such as EljenEJ-254 or Saint-Gobain BC-454 which are both B¹⁰ loaded plasticPVT-based scintillators, or cerium activated Li⁶ doped silicate glassscintillators from Saint-Gobain, although Li⁶ doped plastics have alsobeen fabricated. For the various neutron capture therapy (“NCT”)applications, including both BNCT and GdNCT (gadolinium-NCT), theneutron beams employed span the energy range from thermal-NCT tofast-NCT (also called FNT), but most NCT programs appear to be based onepithermal-NCT. Unfortunately all of these neutrons are also moredamaging to the scintillator material than protons and/or photons, andtherefore scintillator replacement would need to occur much morefrequently. For this reason the internal calibration scheme employed inthe above embodiments is important for the successful implementation ofneutron beam monitors, and the fact that scintillator replacement andinternal calibration could be accomplished within minutes would be evenmore beneficial for NCT than for proton or photon EBRT due to morefrequent replacement. One method to prolong the useful lifetime of theboron doped scintillator, and therefore not have to replace it as often,is to integrate a motorized X-Y translation stage into the beam monitorenclosure structure and thereby translate the entire system in the X-Yplane in relatively small steps as required, thus moving it around theisocenter and lengthening the period between scintillatorreplacement—this strategy is conceptually similar to moving thescintillator-frame in small steps in the 6-way-cross via the previouslydescribed push-pull linear positioners.

A general complication associated with scintillators for neutrondetection is that most neutron sources also generate gammas, andscintillators that detect neutrons will therefore also detect gammas.Most applications, be they medical imaging or homeland security, requireneutron detection systems that can effectively discriminate betweengammas and neutrons. The disclosed beam monitor embodiments in FIGS. 18and 19 can effectively provide such discrimination for NCT applicationssuch as BNCT and GdNCT, as well as for other applications such ashomeland security. The method by which this can be achieved is to usetwo different scintillators, as configured in FIGS. 18 and 19 , wherefor example the scintillator on one side (e.g., entrance window) such as1862 and 1962 respectively might consist of either a thin BoPEN film ora conventional polyvinyl toluene (“PVT”) or polystyrene (“PS”) basedgamma/ion scintillator, with the scintillator on the opposite side(e.g., exit window) such as 1860 and 1960 respectively being a neutronsensitive scintillator such as the boron loaded EJ-254 based PVT (˜5%natural boron) or BC-454 based PVT (˜5% natural boron, although 10%natural boron is also available). The method to separate the neutrongenerated image/signal from that produced by gammas is to digitallysubtract the image/signal generated by the 1862 or 1962 scintillatorfrom that generated by the 1860 or 1960 scintillator. Such a design willmimic or behave as though it has a high level of gamma to neutrondiscrimination.

In looking into scintillator damage by neutrons, the issue of radiationdamage to the beam monitor cameras was also investigated. Experimentsindicate that the slow radiation damage over a period of years to thepatient viewing cameras in proton therapy treatment rooms is primarilydue to neutrons. The main source of these neutrons is not from theproton beam system, although some neutrons are generated in thecollimator, but from the patient's interaction and absorption of theproton beam itself—i.e. primarily where the proton beam stops at thetumor site inside the patient. Radiation damage to digital cameras hasbeen studied extensively for the imaging sensors used in space astronomy(mostly CCDs), as well as for other situations in which high neutronfluxes are created and monitored by cameras such as for fusion research.It has been found that although shielding of cameras can be helpful, itis also not so straightforward. One solution is the direct cooling ofthe camera sensor to about −20° C. or colder, which also eliminates thecamera as a heat source and thereby reduces thermal heating causingcalibration drift not only of the camera, but also of the UV-LEDs,UV-photodiodes, and possibly even the scintillator response itself.

Camera sensors/electronics are prone to neutron damage because siliconis typically doped with boron to achieve p-type silicon. However, p-typesilicon can also be produced by doping with gallium (“Ga”) instead ofboron, and in this way fabricate radiation-hardened silicon devices.Both radiation-hardened and radiation-tolerant semiconductors, includingCMOS image sensors and cameras are available from several sources, assuch sensors and cameras are required for a number of applicationsincluding military, aerospace, scientific, and nuclear energy. Withconventional boron doped silicon devices, the primary camera visualdamage due to neutrons is the creation mostly of “bright” pixels in thesilicon image sensor. The “bright” pixels caused by rad-damage are highdark-current pixels or “hot-pixels”. Some embodiments replace thecameras in the beam delivery room every couple of years. The majority ofneutrons created are scattered in the proton beam momentum direction,which is towards the opposite side from where the patient is beingirradiated and thus towards the back of the room. However the entireroom is effected by the scattered neutron field and some neutrons willbackscatter towards the cameras located at the beam nozzle exit and infront of the patient. Frequent internal calibration of the beammonitoring system will identify the radiation damaged pixels, and sotheir contribution to the image analysis can be conveniently eliminatedby software. Partial neutron shielding of the cameras can be achieved byseveral means, including the use of boron doped transparent plastics infront of the camera body and lens, similar to commercially available 5%boron doped PVT plastic scintillators but without the addition of afluor dopant. Since the cameras themselves are located out of the directbeam path, the entire light-tight camera box enclosure, excluding theentrance and exit window areas, can be fabricated out of a neutronshielding metal sheet such as a boron-aluminum alloy like BorAluminumfrom Ceradyne (˜4.5% to 8% by weight of B-10 isotope) or AluBor (10% byweight of natural boron) from S-DH, or a boron clad aluminum such asBORAL or BORTEC. Also boron composite plates made with boron fiber canbe used. Alternatively, a number of small shielding plates can bestrategically placed around each camera body. Another solution forshielding the front of the camera from neutrons is to use a thick, highboron content transparent borosilicate glass (e.g., 3-5% boron) in frontof the camera lens, and maybe in front of the entire camera body. Thereare many borosilicate optical glasses, but Schott N-ZK7 (15% B₂O₃ bywt.), N-BK10 (13% B₂O₃ by wt.) and N-BK7 (10% B₂O₃ by wt., alsoreferenced as Borkron) with 4.7%, 4.0% and 3.1% boron respectively (byweight), or Schott BOROFLOAT-33 with 4.0% boron (i.e., 13% B₂O₃) are allreadily available as is Corning 7740 glass (Pyrex) which is 12.6% B₂O₃.However BOROFLOAT-33 being much more economical than other boratedglasses is sold for neutron shielding in thicknesses up to ˜25 mm. It isnoted that extremely high B₂O₃ and Gd₂O₃ glasses have been described inthe patent literature such as Application PCT/JP2013/069578 whichpotentially would be more effective. Also a source of heavily dopedboron and lithium polyethylene sheets, bricks and rods/cylinders isShieldwerx (a division of Bladewerx LLC), which sells a 30% naturalboron doped polyethylene product called SWX-210 (i.e., contains1.87×10²² boron atoms per cm³) as well as a 7.5% natural lithium dopedpolyethylene product SWX-215. The disadvantage of boron doped neutronshielding materials is that each neutron captured by boron generates a0.42 MeV gamma ray; however, lithium doped shielding materials do notproduce any neutron capture gammas. However the lower neutron capturecross-section of Li⁶ compared to B¹⁰, means that a greater thickness oflithium doped material is required than similarly doped boratedmaterial.

In terms of neutron damage, at what point the cameras, or possibly justthe silicon image sensors, would have to be replaced needs to beexperimentally determined, but most likely it will be in years forproton or photon therapy since the internal calibration system canadjust for bad pixels in real-time as they occur. It is also noted thatthe larger the image sensor pixel size, the less prone it is toradiation damage. For the beamline monitors such as the 6-way-crosses inFIGS. 9-13 , the camera can be moved a significant distance away fromthe beamline and hence the radiation field, with the detrimental effecton photon collection and spatial resolution minimized, by extending theoptical system length. This can be achieved via the introduction of arelay lens system including a relay train assembly. The specific designwill depend on the distance desired for extending the optical tubelength of the camera system. Relay lenses are made to extend the viewingdistance for remote viewing and operate by producing intermediate planesof focus. Collecting and dispensing optical images is done with focusinglenses which transport the light pattern via a relay lens or train ofrelay lenses. Some examples include periscopes, endoscopes, remoteinspection and surveillance. A wide selection of relay lenses arecommercially available.

Embodiments are directed to external beam radiation therapy (“EBRT”)related applications for both particle and photon radiation. For bothtypes of EBRT, the embodiments are directed towards beam monitoringsystems designed for use in either of two locations: (1) internal beammonitors located within the accelerator beam delivery system andtherefore prior to the beam exiting the system nozzle or snout orcollimator, or (2) external beam monitors located outside theaccelerator beam delivery system after exiting the system nozzle orsnout or collimator and thus positioned after the delivery system exitand in front of the patient.

Embodiments can further be used for a variety of industrial andscientific beam monitoring applications such as ion implantationaccelerators (e.g., depending on ion, typically >0.3 MeV), and nuclearphysics particle accelerators. Typically ion beam implantation will havethe most stringent detector/monitor design requirements with regard tobeam transparency, as the ion particle energies are frequently below 1MeV and the particles themselves are typically highly ionized, heavynuclei. Many accelerators used for nuclear physics also operate atrelatively low to medium ion energies, so the same beam monitor conceptin accordance to embodiments can be used for both applications. Someadditional advantages of the described embodiments include the relativelow cost of the beam monitor critical hardware, and the low costlifetime operational/maintenance expense which includes the minimaloverhead expense associated with the ultra-fast internal calibrationsystem, as compared with the time consuming calibration cost forconventional systems. This benefit is also important for scientificapplications (e.g., nuclear physics) that subject otherdetectors/monitors to costly maintenance and radiation damagereplacement expenses.

The therapeutic benefits of embodiments of UFT beam monitors disclosedherein are particularly useful with “FLASH” irradiation therapy in whichshort pulses (≤5 second) of radiation are delivered at ultrahigh doserates of ≥40 Gy/s (i.e., FLASH) compared to conventional dose rates of≤0.03 Gy/s in single doses over a period of 60 seconds. FLASHradiotherapy may well result in a paradigm shift in the treatment ofcancer as ultrahigh dose rates appear to increase the differentialresponse between normal and tumor tissue, thus increasing the lethalityto malignant cells while not significantly increasing damage to healthycells. In order to monitor the FLASH beam in real-time, the much fasterbeam profile imaging time and readout capability, greatly improvedintrinsic 2D position resolution, and the much higher dose ratecapability of the described UFT beam monitors yields order-of-magnitudeadvantages when compared to conventional ionization chambers, and inthis sense appears to be an unexpected enabling technology.

Additional embodiments for beamline monitors based on the 5-way and6-way-cross configurations previously described in FIGS. 6-13 and FIG.27 are now disclosed. Specifically, FIGS. 28A-C illustrate a system thatincludes a scintillator-frame beam monitor holding three separatescintillator films in a 6-way-cross vacuum chamber with a camera in anattached 4-way-cross open system capable of actively or passivelycooling the camera in accordance with embodiments. FIGS. 28A-Cillustrate a system 2800 that includes a segmented ladder type ofscintillator film holder 2844 in FIG. 28A which can hold at leastseveral different scintillator frames 2840 that can be pushed into thebeamline center from left to right by the push-pull linear positioner2872 which is enclosed in a nipple 2890. The segmented ladderscintillator film holder embodiment shown in FIGS. 28A-C holds threescintillator frames, but in other embodiments can hold more if eachscintillator frame is either smaller as in FIG. 29A, or if the nipplelength is longer and can accommodate a larger size segmented ladder. Theembodiment shown in FIGS. 28A-C includes a larger tube diameter4-way-cross 2815 attached to the vacuum viewport assembly at the top ofthe smaller tube diameter 6-way-cross. The larger tube diameter4-way-cross assembly encloses the machine vision camera 2804 withattached lens 2806. FIG. 28B is a perspective view of system 2800, inwhich the camera body 2804 is attached to heat sinks on four sides forpassive cooling of the camera body. FIG. 28B shows two of the flanges2817 and 2818 left open of the 4-way-cross with top flange 2816 alsoleft open for natural passive convective air cooling over the coolingfins of the camera heat sinks. However, for more efficient activecooling of camera 2804, the larger tube diameter 4-way-cross of FIGS.28A-C is designed so that it has enough room to accommodate an activecooling system such as a Peltier TE (i.e., thermoelectric) coolingassembly. For active cooling, the 4-way-cross 2815 can accommodate twofans (not shown) attached to the side flanges 2817 and 2818, with alarger size, third fan (not shown) mounted to the top flange 2816. Thesefans can operate either in the blower or exhaust modes and most likelywill be some combination of both with cool air being blown in and hotair being exhausted out. Using a relatively inexpensive 50-watt PeltierTE active cooling fan assembly in experimental testing, a test camerasensor board temperature was reduced by ˜25° C. which is important toreducing sensor noise when taking long camera exposures. If moreeffective camera cooling is required, then instead of the larger tubediameter 4-way-cross as described above, a 6-way-cross could be usedinstead, which would provide two additional flange openings for eithermore efficient air circulation by convection or two additional ports foractive fan cooling on all four sides of the camera body. Also, by usingeven larger tube diameters, then multiple Peltier TE active cooling fanassemblies could be used.

For beam monitors that employ polymer based scintillators such asdescribed herein, that are to be used or inserted in an ultra-highvacuum (UHV) beamline such as in the 6-way-cross CF-flanged systemsdescribed above, the polymer based material (depending on itscomposition and surface area) could have too high an outgassing rate tobe UHV compatible. In order to reduce the outgassing rate from suchscintillator polymer films to a manageable level, they could beeffectively encapsulated or “sealed” and made UHV compatible by coatingboth the front and back film surfaces with an optically transparent, lowoutgassing, thin-film layer (e.g., ≤0.5 μm thickness) such as Al₂O₃.Alternatively, if one side of the polymer scintillator is thin-filmmetallized, for example to create a reflective back surface and therebyenhance photon emission out of the front surface, then only the photonemitting surface would need to be thin-film “sealed” as described abovewith a coating such as Al₂O₃.

The perspective drawing of FIG. 28B provides a good view of the6-way-cross 2801 entrance flange through which the particle beam entersas it passes through the center scintillator frame. Also shown in FIGS.28B and 28C is the camera light-blocking disk/plate 2808 located betweenthe camera body 2804 and camera lens 2806, which blocks light that canenter the 4-way-cross through the open flanges 2816-2818 from findingits way into the camera though the lens 2806. The UV-light generatedfrom a UV-source (not shown) such as a UV-LED attached to the supportring 2809 can be blocked from reaching the camera sensor by aUV-blocking and visible transmitting filter (not shown) attached to thecamera lens 2806. Also attached to the support ring 2809 is aUV-photosensor (not shown) such as a UV-photodiode for each UV-sourcefor monitoring and/or calibrating the UV-source intensity. FIG. 28Cprovides a frontal perspective view at a different angle of the4-way-cross 2815 that encloses the camera assembly.

FIGS. 29A-B illustrate a system that includes a scintillator-frame beammonitor holding six separate scintillator films in a 6-way-cube vacuumchamber with a camera in an attached 4-way-cross open system capable ofactively or passively cooling the camera in accordance with embodiments.The embodiment shown in FIGS. 29A-B illustrates a system 2900 that issimilar to that described for FIGS. 28A-C, and shares most all of thesame component/element features, but with the following differences.Instead of system 2900 being based on the 6-way-cross 2801 in FIG. 28 ,it is based on a 6-way-cube 2901. Further, the segmented ladder type ofscintillator film holder 2944 in FIGS. 29A-B is shown to hold sixdifferent scintillator frames with each scintillator frame 2940 having asmaller scintillator area as can be seen in comparing the scintillatorframe area in FIG. 29A to that in FIG. 28A. Otherwise the componentdescriptions for system 2800 apply to system 2900. The primary advantageof the 6-way-cube structure is that four of the six sides provide closeraccess to the center of the beamline than in the 6-way-cross andtherefore results in a more compact structure that can potentially be anadvantage in allowing closer placement of the camera and PMT to thescintillator. However, depending on the application, the cube basedstructure can also be a disadvantage in terms of a somewhat shorterlength for the segmented ladder scintillator film holder and the factthat there can be no rotatable flanges built into the 6-way-cube,whereas the 6-way-cross can have one or two rotatable flanges on eachaxis.

The camera used for the photograph of FIG. 26 was a Basler AceacA2040-120 um with 8.9 mm diagonal (i.e., 7.1 mm×5.3 mm) 3.1 MPresolution CMOS image sensor, corresponding to a 1/1.8″ image circle.The lens used was relatively inexpensive $75 lens (i.e., not a macrolens) having a matching 1/1.8″ image circle with an aperture of F/2 anda focal length of 4 mm. The lens front optical element was ˜110 mm fromthe target center (i.e. working distance) on exactly a 45° line.However, the horizontal line of the 10 cm outlined square at the bottomof FIG. 26 , which could represent the top of the scintillator filmclosest to the camera in FIGS. 28A and 29A, was only ˜87 mm from thelens front optical element yet remains in focus even given the largeperspective tilt distortion and close focus distance. In this regard,the maximum size scintillator film 2840 in FIG. 28A that can be viewedthrough the 8.9 cm diameter viewport window of the 6-way-cross 4″ tubeO.D. in FIGS. 28 and 29 is ˜7.6 cm×8.2 cm. Given the excellentdepth-of-field at this close working distance, which is compatible withthe embodiments illustrated in FIGS. 28 and 29 , an analysis of thisfigure/photograph indicates that a conservative estimate of the imageposition uncertainty or position accuracy is one-half the calculatedcamera sensor pixel field-of-view (FOV) and for this camera-lenscombination at this 110 mm working distance the calculated pixel fullFOV is 92 μm, so one-half would be 46 μm. However, much higher pixelresolution cameras are available with CMOS sensor resolutions in therange of 12-25 MP, which would yield a much smaller FOV withsignificantly better position accuracy.

As can be seen in FIG. 26 , a 7.6 cm×8.2 cm rectangular area would fitroughly midway between the 5 cm and 10 cm outlined squares and wouldtherefore fall well within the field-of-view and the depth-of-fieldfocus of the described camera-lens system. However, for a confined beamsuch as in the 4″ tube in FIG. 28A with a 7.6 cm×8.2 cm object field, ahigher resolution camera than used for FIG. 26 could be employed. Anexample of one such camera is the 12.2 MP Basler acA4024-29 um combinedwith an 8 mm focal length lens at a working distance of 100 mm, whichcould achieve a full pixel FOV of ˜21 μm. If used with a tightlyfocused, stationary beam such as an electron beam confined to a 2″ tube,then the same 12.2 MP camera combined with a longer 16 mm focal length,high resolution lens (e.g., ˜150 line-pairs/mm), at the same 100 mmworking distance should realize a full pixel FOV and resolution of ˜10μm, corresponding to an absolute position accuracy of ˜5 μm. Forexample, FIG. 32 is a reconstructed image showing the beam position,shape and intensity profile of a circularly orbiting electron beamphotographed off of an oscilloscope scintillator screen and captured in21 μs to minimize the beam image blur caused by the circular beammovement in accordance to embodiments. The pixel field-of-view is ˜30 μmwith an estimated 2-3 μm spatial resolution. The 3D image in FIG. 32employed the same 3.1 MP machine vision camera (i.e., 2048×1536 pixelCMOS sensor) as used in FIG. 26 , but with a 6.1 mm focal length lensand demonstrates that such a camera-lens system as in many of theembodiments described herein is capable of capturing particle beamimages in real-time off of a scintillator film providing not only thebeam position and half-bandwidth (i.e., FWHM), but the full band shapeand intensity profile over 3 orders-of-magnitude (i.e., 12 bits) andthereby also capturing the beam tail. An analysis of FIG. 32 indicatesthat the image position accuracy is ˜15 μm corresponding to one-half thefull pixel FOV. The FWHM for this figure is ˜10 pixels corresponding to˜300 μm. The beam position is defined in FIG. 32 by its two-dimensional(2D) location in terms of its X and Y pixel coordinates in the figurelegend which can be calibrated to its absolute location on thescintillator screen. The beam centroid center-of-gravity position, aswell as the beam width from the calculated Gaussian fit, was determinedto have about a 2-3 μm spatial resolution and with a higher pixelresolution camera the reconstructed image position and width uncertaintycan likely be reduced to within ≤1 μm.

As discussed above, FIGS. 26 and 32 provide visual confirmation that thetransmissive ionizing-radiation beam monitoring system embodimentsdescribed herein for EBRT applications, such as those illustrated inFIG. 14-22 and FIG. 30 , are optically capable of generating highresolution beam images. Given the same size camera CMOS image circle of1/1.8″, but at the longer average working distance of ˜170 mm for thefolded optical path of each camera in FIG. 30 as compared to the 110 mmin FIG. 26 that was used to replicate the approximate working distancein the 6-way-crosses shown in FIGS. 28 and 29 , the field-of-view willbe proportionately larger and will more than cover the largerscintillator areas in the aforementioned EBRT figures and embodimentssuch as in FIG. 30 . A reasonable full-size scintillator area for theEBRT applications could be on the order of about 26 cm×30 cm, but ifcovered by four cameras each focused on one quadrant as in FIGS. 17, 19,20 and 30 , the minimum field-of-view for each camera would be 13 cm×15cm which can be seen as partially covered in FIG. 26 at a workingdistance of just 110 mm. Even without going to a larger CMOS sensorcamera, the longer average working distance of 170 mm in the referencedfigures will allow the same camera-lens setup to more than cover thislarger scintillator area even when taking into account that the closestdistance from the camera lens to the top scintillator horizontal edgewill be ˜130 mm. In fact, the optics work out that a somewhat longerfocal length lens with a higher pixelated camera CMOS sensor could beused to realize better pixel resolution than for the previouslyreferenced 4 mm focal length lens.

FIGS. 30A-C illustrate a system that includes an eight camera, full-sizedouble window/scintillator sliding-frame module beam monitor in alight-tight slim enclosure in accordance with embodiments. Theembodiment illustrated in FIGS. 30A-C, which illustrates system 3000, issimilar to that for system 1900 as shown in FIGS. 19A-B and shares mostall of the same features, but with a few important differences. Bothsystems 1900 and 3000 illustrate an eight camera, full-size doublewindow/scintillator frame module beam monitor in a light-tight slimenclosure in accordance with embodiments. Although the eight camera-lensunits are arranged somewhat differently in the two systems, both systemsemploy four cameras per scintillator, with one mirror 3030 and 3032 inclose proximity to each camera lens 3040 and 3042 as shown respectivelyin FIGS. 30A and 30C, and with all eight mirrors located out of theincident ionizing radiation beam path and obliquely facing both the lensand the scintillator at an angle. Thus each machine vision camera-lensunit and its associated close proximity mirror comprises a foldedoptical system configuration with respect to its view of one section orquadrant of the scintillator surface to reduce a thickness or depth ofthe light-tight enclosure with a projection of its optical axis orientedat an angle of incidence of 45°±35° to a surface of the scintillator.Further, both systems are designed so that they can accommodate one ormore UV-sources (e.g., UV-LEDs) 3050 and 3051 in FIG. 30A and one ormore UV-photosensors (e.g., UV-photodiodes) 3052 and 3053 in FIG. 30Afor internal system calibration which includes monitoring eachscintillator for radiation damage. A major difference between systems1900 and 3000, besides the different camera arrangement, is in thedesign of the entrance and exit window/scintillator frame modulesystems. In system 1900 the two window/scintillator modules 1962 and1960 can be replaced from outside the light-tight enclosure asillustrated in detail in the embodiment shown in FIG. 14B. Morespecifically, the outer retaining frame 1410 is first removed and thenthe window/scintillator replacement module 1460 is dropped into therecessed frame of the cover plate 1414 with the outer retaining frame1410 then replaced. However, for the embodiment in FIGS. 30A-C, thewindow/scintillator module 3023 is attached to the sliding plate frame3025 and then the combined window/scintillator plate assembly is slidinto a track or channel in the top cover plate 3010 as shown by thedotted arrow in FIG. 30B and viewed in FIGS. 30A and 30C. The samedesign for replacement of the window/scintillator in the bottom coverplate 3020 is also shown in FIG. 30A in which window/scintillator module3022 is attached to the sliding plate frame 3024. The advantage of thesliding window/scintillator system in which access and replacement ofthe window/scintillator module occurs from the side of the light-tightslim enclosure, is that for many EBRT systems it might not be easy togain access to the front or back cover plates for fastwindow/scintillator replacement.

The dual scintillator beam monitoring system 3000 illustrated in FIGS.30A and 30C, as well as systems 1800 and 1900 illustrated in FIGS. 18A-Band 19A-B, with each scintillator optically coupled to its own set ofcameras and integrated with its own computing platform, be it via cameraembedded FPGAs, frame grabbers or computers, comprise two independentbeam monitoring detection units within a single enclosure/structure,with each unit having its own real-time data processing and analysiscapability. The described embodiments identified as systems 1800, 1900and 3000 therefore each constitute an integrated system with built-ininternal redundancy. However, if so desired the data from the twoindependent beam monitoring detection units could be combined (i.e.,added together) by means of data synthesis and meta-analysis to yield alarger unified/pooled data set with enhanced statistics for improvedprecision, accuracy and resolution for tracking the beam movement andgenerating the beam position, beam intensity profile, beam fluence, andexternal dosimetry.

FIG. 31 illustrates a method to avoid loss of data during the readoutdead-time in a dual-scintillator multiple machine vision camera systemby introducing a time-delay in the camera sensor readout sequencebetween the two scintillator camera systems in which the two sets ofcameras are time-shifted in their shutter exposures by approximatelyone-half of a time-frame so that one set of cameras is always collectingdata during the dead-time readout period of the other set of cameras inaccordance with one embodiment. The two independent beam monitoringdetection units as described immediately above, with their two sets ofcameras, can be configured such that their respective data sets aretime-shifted in their frame sequences with respect to each other asillustrated in FIG. 31 , resulting in the two sets of streaming databeing out-of-phase or time-displaced one relative to the other by afraction of a frame. FIG. 31 shows one such example with eachscintillator-camera system operating at a frame rate of 10,000 fps(i.e., frames per second), corresponding to 100 μs per frame andconsisting of a 90 μs exposure window (i.e. shutter speed) and 10 μs ofdead-time allocated to CMOS readout and digitization. In general, a morerealistic dead-time would be ≤5 μs with a corresponding shutter speed orexposure time of ˜95 μs. By configuring the above two independent beammonitoring detection units with their two sets of partially overlappingtime-shifted streaming data by a fraction of a frame as shown in FIG. 31, one set of cameras will always have their shutters open and theirimage sensors recording emitted photon data from one scintillator duringthe dead-time sensor readout and digitization period of the other set ofcameras associated with the other scintillator. Therefore, by staggeringor off-setting the two sets of streaming data in this manner, the shortperiod of total blindness to the incident ionizing-radiation due to thecamera image sensor dead-time in one system can be covered and recordedin the second system.

In accordance to embodiments, the entrance and/or exit ultra-thinwindows of the beam monitor enclosure can be dark colored or black tominimize internal photon reflections from the emitting scintillatormaterials and/or UV-LEDs, but can also be a dull or even shinyreflective ultra-thin, low density, low-Z metal such as an aluminum ortitanium foil if the internal beam monitor reflectivity is properlycalibrated and/or taken into account. Even for a black coated aluminumfoil window, continuous exposure to a particle beam could ablate orsputter off some of the black coating which is typically ˜2 μm thick andthus reduce photon absorbance and increase reflectivity as a function ofintegrated beam exposure time and so should necessitate regularmonitoring and/or calibration with eventual replacement. This is onereason why the window and scintillator might best be assembled as asingle window/scintillator frame module as previously described in whichboth components (i.e., window and scintillator) can be convenientlyreplaced at the same time.

In applications for which the particle beam is electrons, because oftheir low mass relative to a proton, the scattering of the incidentelectron beam in passing through the beam monitor material is moresignificant than for protons. Therefore to minimize scattering of anincident electron beam, such as in electron FLASH RT (“eFLASH”), thebeam monitor material thickness and density should be as low aspossible. In practical terms, for large-area windows (e.g., ˜1 ft²)ultra-thin aluminum foils are an excellent choice although titaniumfoils might be superior because they are stronger and in thicknesses of0.0005″ are essentially defect and wrinkle free which is not true foraluminum foil in this thickness. However a thin-film metal coating(e.g., ˜0.1-0.2 μm) on a polymer film base could be even better,especially if also coated black or coupled to an ultra-thin blackpolymer film. Metallized polymer films with the polymer base being asthin as ˜1-2 μm are available in large size continuous rolls with widthson the order of 1 meter, as are black polymer films as thin as ˜5 μm,thus a layered composite window of ultra-thin black polymer coupled to ametallized polymer could have a total thickness of ˜7 μm, whileultra-thin aluminum foils are commercially available in continuouslengths in roll widths of ˜48″ to 60″ and in thicknesses as small as 6μm. Black coated aluminum foils are available in thickness of ≥14 μm(i.e., with the foil being ˜12.7 μm and the matt black coating being˜1-2 μm). With scintillator films such as BoPEN (biaxially-orientedpolyethylene naphthalate) as thin as 3 μm, which have been tested andfound to be both satisfactory and highly radiation damage resistant asseen in FIG. 3 , the total material thickness of the describedembodiments could be sufficiently small so that to first order it couldbe almost ignored with respect to the beam monitor material contributionto electron beam scattering, beam energy loss and intensity loss forelectron based EBRT modalities such as eFLASH. More specifically, forthe range of electron energies currently projected for eFLASH (e.g.,approximately 4-20 MeV), and with a total minimum beam monitor materialthickness equivalent to ˜20-35 μm of aluminum, the beam energy loss andelectron scattering will be practically negligible in comparison to theenergy loss and scattering of the electron beam in passing through 1meter of air. For example, the energy loss for a 20 MeV electron beam inpassing through a 35 μm thickness of aluminum foil will be ˜22 keV(i.e., 0.11% loss), as compared to an energy loss of ˜305 keV for thesame beam passing through 1 meter of air (density of 0.0012 g/cm³ fordry air at 20° C. at sea level). In other words, the energy loss throughtwo aluminum foil windows and a few microns of scintillator film will bejust 7.2% of the energy loss for the same beam in passing through 1meter of air. For a 4 MeV electron beam, the energy loss through thebeam monitor will be ˜15 keV (i.e., 0.38% loss), as compared to a 222keV energy loss through 1 meter of air, which corresponds to the beammonitor energy loss being just 6.8% of the energy loss through 1 meterof air.

High energy electron beams generated by linear accelerators (linacs)have been used for almost 50 years to treat cancer by EBRT. As indicatedabove, the clinical linacs used for electron RT (radiation therapy)generally cover the energy range of 4-20 MeV. The distal depth of 90%maximal dose (d90) for electron-RT corresponding to the 4 MeV to 20 MeVenergy range is 1.5 cm and 6.1 cm respectively. For treatment of tumorsbeyond ˜6 cm, clinical electron linacs with energies >25 MeV arerequired but have not been developed for clinical use (e.g. energies of≥100 MeV might be needed for deep-seated, large, dense tumors in theabdomen and pelvis). To treat such tumors by EBRT, photons/X-rays,protons and ions (e.g., He and C ions) are preferred and clinicalmachines for both photons and protons have been commercially availablefor decades. Thus for relatively shallow tumors eFLASH is being pursuedand has been demonstrated with very favorable results in the first humantest reported in 2019. However, for more deep-seated tumors proton-FLASHand photon-FLASH machines are more appropriate with proton therapymachines now being modified for proton-FLASH for clinical testing.

Novel EBRT modalities continue to be conceived, researched and evaluatedfor clinical translation and human trials. Therefore, besides thevarious EBRT modalities discussed above and listed in the “BackgroundInformation” section, several novel spatial-temporal modalitiesincluding some that can exploit the FLASH effect to some degree withspatial grid separation are being investigated and could benefit by theinventions and embodiments described herein, including GRID, LATTICE,minibeam and microbeam radiotherapy (“RT”) in addition to FLASH-RT whichhas been previously described. For microbeam-RT (“MRT”) the ionizingbeam used in animal studies has typically had a half-bandwidth on theorder of ˜25-50 μm with about a 200-400 μm pitch or spacing betweenadjacent peak centers. The ionizing-radiation has been almostexclusively high energy X-ray photons from one of only a few suchcapable synchrotron sources in the world. Therefore, for a practicalsystem in a clinical setting a compact, high flux, photon source isneeded than can deliver dose rates on the order of 50-100 Gy/s orgreater. Several companies and academic groups are pursuing thischallenge, but it is still many years in the future and for this reason,protons and heavier ions such as helium and even carbon are beingevaluated for MRT because such sources could be easier to develop andhave the additional advantage over photons of maximum energy depositionat the Bragg peak with a sharp intensity fall-off thereafter. As a morepractical alternative to MRT, proton minibeam-RT (pMBRT) has beendemonstrated using typical beam widths in the range of 0.4 mm to 0.7 mmwith very favorable results such that preparations for the firstclinical trials are now being made in Europe and with heavier-ions alsounder consideration. One problem with the lightest particles such aselectrons and protons for MRT is that they are the most prone toscattering and if having to traverse deep into the body they wouldscatter or smear so much as to significantly lose their microbeamspatial integrity. Nonetheless, many of the embodiments described hereinare capable of meeting the temporal and/or spatial requirements neededfor essentially all types of photon and particle EBRT modalities withprecise beam position, shape and dose analysis in real-time. Aspreviously discussed, some of the embodiments described using relativelylow-cost cameras and lenses in both single and multi-camera beammonitoring systems should be able achieve spatial resolutions on theorder of microns depending on the application and the size of the objectfield. In contrast, there are no existing commercial ionizing-radiationbeam monitors with the real-time temporal and spatial resolution thatcan match that of the embodiments described herein, while also beinghighly transmissive with large-area capability (e.g., ˜1 ft²) and highlyradiation damage resistant, all at relatively low cost.

Because of the relative proportionate increase in beam scatteringassociated with the higher spatial resolution narrow-beam modalitiesdiscussed in the previous paragraph, if the ionizing-radiation iselectrons or even protons the spatial resolution of the beam candeteriorate rather quickly even in air, and especially for MRT. Sincephotons scatter much less than electrons or protons, photons have beenthe ionizing-radiation of choice for MRT with beam diameters on theorder of 25-50 μm. For this reason heavier ions than protons, such ashelium and carbon are being considered for MRT. Yet even for photons,the beam scattering in the patient can be significant if the tumor isdeep-seated. Therefore to minimize the scattering in air forsubmillimeter spatial resolution multibeam modalities the beam source isgenerally positioned as close to the patient as possible. This meansthat for high spatial resolution multibeam modalities there is likelynot enough space to place the previously described beam monitors betweenthe radiation source/collimator and the patient. However, by employing anew system configuration and method, the light-tight enclosed beammonitors previously described can be configured for use in patienttreatment planning, diagnostics, analysis, dosimetry and qualityassurance (QA). The novel method and system embodiment illustrated inFIGS. 33A and 33B describe two versions of system 3300 that can be usedwith appropriate phantoms to measure beam shape, intensity profile,fluence and dosimetry, as well as loss in beam definition due toscattering and absorption as the beam of ionizing-radiation passesthrough a patient phantom. The described method and system for treatmentplanning and patient QA can be used with essentially all EBRTmodalities, including the temporal and spatial modalities describedabove of FLASH RT, LATTICE-RT, GRID-RT, minibeam-RT and microbeam-RT,with photons, electrons, protons and ions, and for streaming images atrates of 10,000 fps (i.e. 100 μs per frame) and beam widths as narrow as25-50 μm.

FIGS. 33A-B illustrate a system and method in which anionizing-radiation beam source with two separated ultra-thinscintillator based multi-camera beam monitors can be used with a patientphantom or material cross-sectional phantom placed between them forpatient treatment planning, analysis and quality assurance including 2Dmeasurement of beam scattering, loss of beam quality/sharpness, and beamfluence as the beam penetrates the phantom for both single beam and gridseparated multibeam high spatial resolution radiotherapies (RT) such asminibeam-RT and microbeam-RT in accordance to embodiments. The twoversions of system 3300 illustrated in FIGS. 33A and 33B are both basedon the use of two highly transmissive beam monitors 3310 and 3320separated by an adjustable air volume/gap as indicated by the two narrowdotted arrows going through the beam monitor 3320 indicating that thebeam monitor can be slid back and forth as required on the open frametrack/channel structure 3330 and 3340 which also serves to keep the twobeam monitors aligned with respect to one another. The space between thetwo beam monitors is to allow insertion of either a patient specificphantom such as 3350 in FIG. 33A or an adjustable thickness and densityphantom 3370 as shown in FIG. 33B that includes one or more materialplates that can be of different densities and thicknesses as indicatedby plates 3371-3375. In either case, the volume of air between the twobeam monitors is minimized by positioning the phantom 3350 or 3370 asclose as practical to beam monitor 3310 and then sliding beam monitor3320 close up to the phantom on the opposite side. The beam ofionizing-radiation, as indicated by the short and wide dotted-dark grayarrow 3380, enters beam monitor 3310 through ultra-thin window 3311 andexits through the scintillator/window module 3312, then passes throughthe phantom media before entering beam monitor 3320 through thewindow/scintillator 3322 and exiting through the ultra-thin window 3321as indicated by the lighter-gray short and wide dotted-arrow 3390.Photons generated by the ionizing-radiation beam 3380 passing throughthe beam scintillator 3312 are collected and imaged by one or morecameras, such as 3315, viewing the scintillator through a closeproximity mirror 3316 at an oblique angle that constitutes a foldedoptical system located outside of the beam path and with a projection ofthe camera system optical axis oriented at an angle of incidence of45°±35° to a surface of the scintillator. The same scintillator andfolded optics camera system arrangement is employed for theionizing-radiation beam as it passes through the exit beam scintillator3322. The beam monitors themselves can be essentially any of thelight-tight enclosure beam monitor embodiments previously describedincluding both single and dual scintillator systems, although for mostpatient planning, analysis and QA applications the single scintillatorembodiments 3310 and 3320 would likely be the most appropriate.

In comparing the machine vision camera captured images of theionizing-radiation beam generated at the entrance beam monitor 3310versus at the exit beam monitor 3320 with different phantom mediainserted in between the two beam monitors, one can measure intwo-dimensions the extent of beam intensity reduction and spatialdistortion/smearing including degradation of the beam definition interms of beam shape/width, sharpness, scattering, intensity profile andfluence. In fact, by inserting a succession of different material platethicknesses and densities as illustrated by 3370 in FIG. 33B, theprogressive degradation of the beam definition and intensity profile canbe measured as a function of beam penetration depth through differenttypes of simulated body tissue. This method of analysis in tracking beamdegradation through an adjustable plate phantom could prove to beespecially useful for patient planning and QA with high spatialresolution ionizing-radiation beam modalities involving both singlebeams as well as a grid of multiple beams such as employed withminibeam-RT and microbeam-RT.

The range of appropriate material densities for use as the adjustableplate phantom 3370 in FIG. 33B to simulate a patient's body/organs beingexposed to an incident ionizing-radiation beam can be realized using avariety of polymers/plastics and even metal plates. The materials useddo not have to be optically transparent since the cameras view thescintillators obliquely from the sides. Most fortunately,plastics/polymers are available in a wide range of densities that coverthe human body from fat to bones, for example from 0.9 g/cm³ usingpolypropylene, to 1.8 g/cm³ using PVDF (i.e. polyvinylidene fluoride orKynar-740). However, a magnesium (Mg) plate has about the same densityas PVDF (˜1.8 g/cm³) which is close in density to that of the humanskull and bones, but with Mg having the benefit of being a metal in thesame Periodic Table Group as Ca, with a higher average-Z (i.e. atomicnumber) than PVDF and a lower-Z than Ca, although a good match to whatmight be considered the average-Z of the chemical composition of theskull and bones.

In summary, some of the advantages of the novel beam monitoring systemtechnology and embodiments disclosed herein include: (1) a very smallmonitor thickness in the beam path that combined with its low-Z materialand essentially perfect uniformity provide practically negligibleinterference with the beam and minimal stray radiation in contrast withthe existing devices; (2) a large dynamic range or bandwidth of 2D beamfluence/dose measurements that allows for precise beam intensitymeasurements and dosimetry for low, standard and very high beam rates (ala FLASH); (3) an ultra-fast true 2D beam profile imaging capabilitywith ≤5 μm spatial resolution and ˜50 to 100 μs timing resolution whichis greatly superior in comparison to existing beam monitors based onionization chamber arrays and impossible with strip/wire ionizationchambers.

As previously disclosed, the beam monitor system 2800 in FIGS. 28A-Cincludes a camera 2804 mounted in a 4-way-cross open chamber 2815attached to the 6-way-cross of system 2800. As illustrated in FIGS.28A-C, the 4-way-cross chamber 2815 is open to the air and capable ofactively or passively cooling the camera 2804 in accordance withembodiments. Because the camera chamber is open to the air, it does notneed to be in a vacuum chamber enclosure. Embodiments include the cameramounted in any type or shape structure or enclosure, including a plasticor metal box, a modified cylinder, a circular truncated cone, etc. oreven a 3D printed plastic enclosure of irregular shape.

For particle beam monitoring applications in a high- to ultra-vacuumenvironment using any type of vacuum chamber configuration, includingthe multi-arm crosses shown in FIGS. 9-13 and 27-29 , it is beneficialto reduce internal light reflections as much as possible that result instray photons finding their way into the various light measuring sensorcomponents, such as the cameras, PMTs, etc. The ideal solution is todeposit an ultra-thin black coating (2 μm) on the vacuum chamberinterior walls, which most often are fabricated using stainless steel.For stainless steel there are at least two types of ultra-thin blackcoating technologies that are high-vacuum compatible, “black chrome” and“black oxide”. For a complex tubular structure like a 6-way-cross, itwould be challenging to uniformly coat the insides of the cross usingthe standard black chrome coating process without introducing additionalelectrodes inside the cross. On the other hand, the black oxide processis a wet chemical bath process resulting in a uniform coating on allsurfaces exposed to the bath. The black oxide is actually magnetite(Fe₃O₄) and is chemically formed on the metal surface by chemicalreaction with the iron in the stainless steel. The iron black oxide issubject to chemical reaction with air and moisture, but is protected ina vacuum environment. However, to prevent any surface degradation underambient conditions, the black oxide is typically protected with a verythin layer of oil which is not compatible with vacuum operation. Insteadof oil, a very thin layer (≤1 μm) of parylene can be chemicallydeposited over the iron black oxide. Parylene is considered a very highperformance conformal coating and has been approved by NASA for spaceapplications. It has also been shown to be thermally stable undercontinuous exposure for 10 years at 220° C., so can definitely survive atypical bakeout process at 150-200° C. to eliminate any outgassing ofwhich there would be very little.

The most common pixelated imaging devices and systems are cameras whichare based on relatively small (e.g., from ˜0.2 cm² to 10 cm²) CMOS orCCD silicon photosensors. Silicon-based photosensors are most sensitiveto visible photons, although their spectral sensitivity typicallyextends from the near-infrared to the near-ultraviolet. For higherenergy ionizing-radiation such as X-ray photons, other types ofpixelated sensor systems are used such as flat-panel imagers (FPIs).Most FPIs employ an ionizing-radiation detecting conversion mediumcoupled to a pixelated flat-panel readout backplane of eitheractive-matrix amorphous-silicon (a-Si) thin-film transistors (TFT) orsilicon-CMOS. For large-area X-ray FPIs (e.g., from ˜200 cm² to 2,000cm²), a-Si-TFTs are most often used for the pixelated backplane array,although tiled CMOS sensors have also found application in X-ray imagingsystems that require faster image processing (i.e., frame rates) thancan be achieved with the currently designed a-Si-TFTs. For both types ofsilicon-based pixelated flat-panel readout backplane array systems, theincident ionizing-radiation is typically converted into electricalsignals via the addition of either a direct-conversion orindirect-conversion medium. In other words, the silicon-based pixelatedbackplane array is transformed into an ionizing-radiation imaging deviceby adding a radiation detecting conversion media such as a relativelythin photoconductor (i.e., direct-conversion) or a phosphor/scintillator(i.e., indirect-conversion). Of these two types of media, the mostcommon type for most applications is based on indirect conversionprimarily via organic or inorganic scintillator materials, although forsome specialized applications there are liquid and gaseousscintillators. For direct-conversion, both crystalline andpolycrystalline semiconductor materials are most often employed, someexamples being: amorphous-selenium (a-Se), cadmium telluride (CdTe),cadmium zinc telluride sometimes referred to as CZT (Cd ZnTe), leadiodide (PbI₂), mercuric iodide (HgI₂), lead oxide (PbO), thalliumbromide (TIBr), and various perovskites with some compositions designedfor direct-conversion and other compositions used as scintillators forindirect-conversion. It is noted that for direct-conversion X-ray FPIs,the best materials are relatively high-bandgap (e.g., eV) semiconductorsthat contain elements of high-atomic-number.

In addition to the conventional CMOS or CCD based sensor cameras andflat-panel pixelated imaging systems disclosed above, there are a numberof other types of pixelated imaging detectors and devices that can beconfigured as pixelated imaging systems or cameras. These includevarious types of multi-pixel photon counters (MPPCs) or pixelated solidstate photomultipliers (SSPMs) such as pixelated siliconphotomultipliers (SiPMs) which are a high density matrix/array ofGeiger-mode-operated avalanche photodiodes (APDs) also calledsingle-photon avalanche photodiodes (SPAD). A relatively new type ofpixelated imaging detector/counter is the quanta image sensor (QIS).However, the highest gain (˜10⁶) pixelated imaging detectors aremultianode photomultiplier tubes (i.e., pixelated PMTs) such as the onesfrom Hamamatsu available in either an 8×8 multianode matrix (64 pixels)or a 16×16 multianode matrix format (256 pixels).

Any of the above pixelated imaging detectors can be optically coupled toa suitable imaging lens and with the addition of associated electronicscan be used as the “camera” element, in conjunction with thescintillator screen, for the various transmission ionizing-radiationbeam monitoring systems described herein. In other words, all of theabove imaging detectors could serve the same function as the CMOS or CCDsilicon photosensor in a conventional camera. Therefore, when packagedin a light-tight enclosure with appropriate lens mount, lens, supportingelectronics and software, the resulting pixelated imaging system wouldin essence constitute a novel camera system for which a number ofembodiments and applications are possible—from medical imaging tonon-destructive testing, nuclear physics, high-energy physics,astronomy, etc.

A variety of mostly thin and/or ultra-thin organic scintillators for anumber of different transmissive ionizing-radiation beam monitoringsystem embodiments were disclosed above. However, there are probablymore types of inorganic or ceramic based scintillators than organicscintillators, and inorganic scintillators enjoy the advantage oftypically being much more light yield efficient (i.e., photons perabsorbed MeV) than organic scintillators. Historically, however,inorganic scintillators have not been available as thin scintillators,and certainly not as ultra-thin large-area scintillators, but insteadcan be considered relatively thin scintillators if having anapproximately 1.5 mm or less thickness. The Sigma-Aldrich materialsscience phosphor and luminescent materials online products pages listmore than 300 inorganic phosphor hosts, dopants and products includingnot only bulk materials such as crystals and powders, but alsonanoparticles and about a hundred phosphor dot products. Recently therehas been a lot of interest in various types of perovskite inorganic andperovskite hybrid organic-inorganic scintillators includingdouble-perovskite scintillator materials. Unfortunately, many inorganicscintillators are hydroscopic which makes them harder to work with whenexposed to an ambient environment.

One of the most widely used inorganic scintillators is CsI(Tl), which isonly slightly hydroscopic, but even in small sizes of 2 to 4 cm indiagonal the thinnest single crystal polished material available is ˜1mm thick, with larger sizes being considerably thicker. Nevertheless,for large-area X-ray FPIs of up to ˜60 cm in diagonal, there are severalcommercially available thin or relatively thin inorganic scintillatorscreens based on a few scintillator materials, including micro-columnarCsI having vertically-oriented needle structures (either TI or Naactivated), Gd₂O₂S generally known as gadolinium oxysulfide andabbreviated as GOS or Gadox (either Tb or Pr activated), and ZnS (Agactivated). Typically, these scintillators are deposited on a polymer,or glass, or metal substrate (e.g., aluminum, stainless steel, etc.),and incorporate an ultra-thin protective film covering if hydroscopic,such as a polyester, acrylic, or an aromatic polymer (e.g., parylene) ofless than 10 μm thickness. The most common such scintillator substrateis a polyester sheet of polyethylene terephthalate (PET) of ˜150 to 250μm thickness. The two most widely used scintillator materials forlarge-area X-ray FPIs are CsI(TI) or CsI(Na) with phosphor thicknessesfrom about 0.1 to 0.7 mm, and GOS(Tb) or GOS(Pr) with phosphorthicknesses from about 0.05 to 0.5 mm. It is noted that ZnS(Ag) is alsocommercially available from at least one vendor in a 0.05 mm phosphorlayer thickness on a 250 μm thick polyester substrate.

For X-ray medical radiography including fluoroscopy, the two mostpopular scintillator screen host materials are CsI and GOS, which arecommercially available in sizes up to about 43 cm×43 cm. For securityscreening and industrial inspection, GOS is available in large sheets upto 1.00 m×1.75 m. Both the GOS and ZnS screens are actually a dispersionof very small phosphor crystals embedded in an organic binder/media(e.g., glue, epoxy, etc.). As a consequence, these types of phosphorlayer coatings are sometimes called granular scintillator films. Thereare a number of other potential applications for these scintillatorscreens, such as in nuclear and/or high-energy physics for use inionizing-radiation particle beam tracking, particle beam tuning,spectrometers, hodoscopics, calorimeters, etc. For hodoscopes andcalorimeters, a stack of such scintillator screens might be requireddepending on the type and energy of the incident radiation. This wouldalso be true for calorimeters that might be used for medicalapplications.

In principle, any of the hundreds of inorganic phosphors can befabricated in a similar fashion as the above described GOS scintillatorscreens in which small crystalline particles or nanoparticles aredispersed in an organic matrix (e.g., binder or glue layer) and coatedon an appropriate thin substrate, with or without an ultra-thinprotective layer. A few such possible scintillator materials (usingtheir abbreviated name designations) activated by Ce include: LSO:Ce,LYSO:Ce, GSO:Ce, YAG:Ce, TAG:Ce, GAGG:Ce, GPS:Ce, etc. It is noted thatthe GOS based scintillator screens can be used to advantage in a neutronbeam monitoring system, as Gd has the highest neutron cross-section ofany element on the periodic table. In this regard GSO, GPS and GAGG alsocontain Gd and could be potential candidate materials for thisapplication. As mentioned previously, boron neutron capture therapy(BNCT) and gadolinium neutron capture therapy (Gd-NCT) are being pursuedworldwide for treating some of the most difficult types of cancer tumorsby external beam radiation therapy, so use of Gd containing phosphorscould prove important for monitoring the incident neutron beam.

The use of shielding materials for neutrons has been previouslydiscussed quite extensively. For X-ray medical radiography, as well asfor ionizing-radiation particle beams that generate X-ray photons asthey interact with other materials, it is possible to efficiently shieldthe cameras from such radiation in the light-tight enclosures describedherein. For medical diagnostic X-rays, ˜0.5 mm of lead or ˜0.3 mm oftungsten will absorb/shield ˜95-99% of the incident X-ray photonsdepending upon the X-ray photon energy. For example, in FIG. 8A, FIGS.14C-D, FIGS. 17A-B, FIGS. 20A-B, and FIGS. 21A-B, a small size leadsheet of this thickness could be placed between each camera and theenclosure wall on the side facing the radiation beam source.Alternatively, the enclosure wall itself on the side facing theradiation beam source could be made from 0.5 mm thick lead.

Embodiments include an ionizing-radiation beamline monitoring systemthat includes a vacuum chamber structure with vacuum compatible flangesthrough which an incident ionizing-radiation beam enters the monitoringsystem. Embodiments include at least one scintillator within the vacuumchamber structure that can be at least partially translated in theionizing-radiation beam while oriented at an angle greater than 10degrees to a normal of the incident ionizing-radiation beam; a machinevision camera coupled to a light-tight structure at atmospheric/ambientpressure that is attached to the vacuum chamber structure by a flangeattached to a vacuum-tight viewport window with the camera and lensoptical axis oriented at an angle of less than 80 degrees with respectto a normal of the scintillator; and at least one ultraviolet (“UV”)illumination source facing the scintillator in the ionizing-radiationbeam for monitoring a scintillator stability comprising scintillatorradiation damage.

Embodiments further include a wired cable or wireless data interfaceconnection between the machine vision camera and a computer system toprocess and analyze a train of image data frames streaming in real-timefrom the machine vision camera. Embodiments further include at least oneUV photosensor positioned to monitor the UV illumination source.

In embodiments, the UV illumination source comprises a UV light emittingdiode (“LED”) with a UV bandpass filter optically coupled in closeproximity to each UV-LED and having a maximum spectral transmission in aspectral region of maximum emission from the UV-LED. In embodiments, thevacuum chamber structure comprises a multi-arm cross or other suchmulti-arm or multi-port chamber.

In embodiments, the scintillator is mounted in a frame and attached to ashaft of a push-pull linear positioner that can be pushed or pulled ornudged through the incident ionizing-radiation beam area from one arm ofthe cross or chamber either towards or into an opposite arm. Inembodiments, the scintillator in its frame is oriented at an angle of45±35 degrees to the normal of the incident ionizing-radiation beam andconcurrently a camera optical axis is oriented at an angle of 45±35degrees to the normal of the scintillator.

In embodiments, the scintillator comprises a film or sheet ofbiaxially-oriented polyethylene naphthalate (“BoPEN”) falling within athickness range between 1 μm and 300 μm. In embodiments, thescintillator comprises a sheet of gadolinium oxysulfide (Gd₂O₂S) that istypically activated with one or more of a rare earth element such as Tb,Pr, Eu, Ce, etc.

In embodiments, a number of scintillators are mounted in segmentedladder type scintillator holder with each scintillator in its own frameand positioned into the incident ionizing-radiation beam area by meansof a push-pull linear positioner. In embodiments, each scintillatorframe and the segmented ladder type scintillator holder has anultra-thin black coating along with possibly some surfaces of the vacuumchamber interior to reduce interior reflections and with the blackcoating having minimal outgassing.

In embodiments, the camera is located off of one arm or port of thecross or chamber, and a photomultiplier tube (“PMT”) or solid statephotomultiplier (“SSPM”) such as a silicon photomultiplier (“SiPM”) isattached via a light-tight structure at atmospheric/ambient pressure tothe flange of a second viewport window on the arm or port opposite thecamera. In embodiments, a UV blocking and visible transmitting bandpassfilter is optically coupled to a camera lens and/or the PMT or SSPM withthe bandpass filter having high transmission in a visible spectralemission region of the scintillator.

In embodiments, the camera is replaced by a second PMT or SSPM such thateach PMT or SSPM is viewing opposite surfaces of the same scintillatorwith or without a lens coupled to each PMT or SSPM. In embodiments, afirst condensing lens is located in close proximity to the viewportwindow in the light-tight structure at atmospheric/ambient pressurecontaining the PMT or SSPM, and a second condensing lens is located onthe other side of the same viewport window in the vacuum chamber justbelow the scintillator frame, with the two condensing lenses separatedby the viewport window but facing each other belly-to-belly to capture arelatively large solid angle of light from the scintillator andprojecting it onto a light sensitive area of the PMT or SSPM.

In embodiments, a first scintillator in its frame is located in one armof the cross or chamber and a second scintillator in its frame islocated in the opposite arm of the cross or chamber, with eachscintillator attached to its own push-pull linear positioner, andwherein the first and second scintillators do not have to be identicaleither in composition or in thickness.

In embodiments, at least one gate valve is positioned between at leastone of the scintillator arms and the flange connected to the main bodyof the cross or vacuum chamber such that the gate valve can be closed toallow replacement of the scintillator or scintillators without breakingvacuum in the main body of the cross or vacuum chamber or beamline.

In embodiments, the scintillator film in the beam path comprises a smallarea of a much larger roll-to-roll scintillator feed system in which thescintillator film is wrapped around and stored on a small diameterfeeder-spool located inside the vacuum chamber structure and pulledacross an incident ionizing-radiation beam axis transit area onto atake-up spool that can be advanced by a stepper-motor rotating a take-upspool spindle to move a new section of scintillator film across the beamaxis transit area to replace a previously radiation damaged area asrequired.

In embodiments, a film of the scintillator is comprised ofbiaxially-oriented polyethylene naphthalate (“BoPEN”). In embodiments,an entire roll-to-roll scintillator feeder spool and take-up spoolsystem can be mechanically translated into or out of an incidentionizing-radiation beam transit area without breaking vacuum.

Embodiments further perform the monitoring of a beam ofionizing-radiation in a vacuum beamline in real-time. The monitoringincludes receiving the ionizing-radiation beam in a scintillatorenclosed in a vacuum chamber structure with vacuum compatible flangesthrough which an incident ionizing-radiation beam enters the vacuumchamber structure, wherein the scintillator can be at least partiallytranslated in the incident ionizing-radiation beam using a push-pulllinear positioner while oriented at an angle greater than 10 degrees toa normal of the incident radiation beam, the vacuum chamber structurecomprising a machine vision camera attached to the vacuum chamberstructure by a flange attached to a vacuum-tight viewport window withthe camera and lens at atmospheric/ambient pressure and a camera systemoptical axis oriented at an angle of less than 80 degrees with respectto a normal of the scintillator; with at least one UV illuminationsource facing the scintillator for monitoring a scintillator stabilitycomprising scintillator radiation damage. The multitude of emittingphotons are created by the ionizing-radiation beam passing through thescintillator, some of which emitted photons are captured by the camera.The monitoring causing a train of image data frames streaming out fromthe camera to a computer system, wherein the computer system processesand analyzes the image data streaming from the camera in real-time tomonitor the beam position, intensity profile and/or shape, beam fluence,and/or a position of single particles.

Many embodiments are specifically illustrated and/or described herein.However, it will be appreciated that modifications and variations of thedisclosed embodiments are covered by the above teachings and within thepurview of the appended claims without departing from the spirit andintended scope of the invention.

What is claimed is:
 1. An ionizing-radiation beamline monitoring systemcomprising: a vacuum chamber structure with vacuum compatible flangesthrough which an incident ionizing-radiation beam enters the monitoringsystem; at least one scintillator within the vacuum chamber structure; amachine vision camera coupled to the vacuum chamber structure; at leastone ultraviolet (UV) illumination source facing the scintillator in theionizing-radiation beam; and a wired cable or wireless data interfaceconnection between the machine vision camera and a computer system toprocess and analyze a train of image data frames streaming in real-timefrom the machine vision camera.
 2. The ionizing-radiation beamlinemonitoring system of claim 1, further comprising: at least one UVphotosensor positioned to monitor the UV illumination source.
 3. Theionizing-radiation beamline monitoring system of claim 1, wherein the UVillumination source comprises a UV light emitting diode (LED) with a UVbandpass filter optically coupled in close proximity to each UV-LED andhaving a maximum spectral transmission in a spectral region of maximumemission from the UV-LED.
 4. The ionizing-radiation beamline monitoringsystem of claim 1, wherein the vacuum chamber structure comprises amulti-arm cross or other such multi-arm or multi-port chamber.
 5. Theionizing-radiation beamline monitoring system of claim 4, wherein thescintillator can be at least partially translated in theionizing-radiation beam while oriented at an angle greater than 10degrees to a normal of the incident ionizing-radiation beam; wherein thescintillator is mounted in a frame and attached to a shaft of apush-pull linear positioner that can be pushed or pulled or nudgedthrough the incident ionizing-radiation beam from one arm of the crossor chamber either towards or into an opposite arm.
 6. Theionizing-radiation beamline monitoring system of claim 5, wherein thescintillator in its frame is oriented at an angle of 45±35 degrees tothe normal of the incident ionizing-radiation beam and concurrently acamera optical axis is oriented at an angle of 45±35 degrees to thenormal of the scintillator.
 7. The ionizing-radiation beamlinemonitoring system of claim 5, wherein the scintillator comprises a filmor sheet of biaxially-oriented polyethylene naphthalate (BoPEN) fallingwithin a thickness range between 1 μm and 300 μm.
 8. Theionizing-radiation beamline monitoring system of claim 5, wherein thescintillator comprises a layer of gadolinium oxysulfide (Gd2O2S)crystalline particles that are typically activated with one or more of arare earth element such as Tb, Pr, Eu, Ce, etc. and dispersed in a hostmatrix, and coated on a thin substrate.
 9. The ionizing-radiationbeamline monitoring system of claim 5, wherein a number of scintillatorsare mounted in a segmented ladder type scintillator holder with eachscintillator in its own frame and positioned into the incidentionizing-radiation beam by means of a push-pull linear positioner thatcan be motor controlled.
 10. The ionizing-radiation beamline monitoringsystem of claim 9, wherein each scintillator frame and the segmentedladder type scintillator holder has an ultra-thin black coating alongwith possibly some surfaces of the vacuum chamber interior to reduceinterior reflections and with the black coating having minimaloutgassing.
 11. The ionizing-radiation beamline monitoring system ofclaim 5, wherein the camera is located off of one arm or port of thecross or chamber, and a photomultiplier tube (PMT) or solid statephotomultiplier (SSPM) such as a silicon photomultiplier (SiPM) isattached via a light-tight structure at atmospheric/ambient pressure tothe flange of a second viewport window on the arm or port opposite thecamera.
 12. The ionizing-radiation beamline monitoring system of claim11, wherein a UV blocking and visible transmitting bandpass filter isoptically coupled to a camera lens and/or the PMT or SSPM with thebandpass filter having high transmission in a visible spectral emissionregion of the scintillator.
 13. The ionizing-radiation beamlinemonitoring system of claim 11, wherein the camera is replaced by asecond PMT or SSPM such that each PMT or SSPM is viewing oppositesurfaces of the same scintillator with or without a lens coupled to eachPMT or SSPM.
 14. The ionizing-radiation beamline monitoring system ofclaim 11, wherein a first condensing lens is located in close proximityto the viewport window in the light-tight structure atatmospheric/ambient pressure containing the PMT or SSPM, and a secondcondensing lens is located on the other side of the same viewport windowin the vacuum chamber just below the scintillator frame, with the twocondensing lenses separated by the viewport window but facing each otherbelly-to-belly to capture a relatively large solid angle of light fromthe scintillator and projecting it onto a light sensitive area of thePMT or SSPM.
 15. The ionizing-radiation beamline monitoring system ofclaim 5, wherein a first scintillator in its frame is located in one armof the cross or chamber and a second scintillator in its frame islocated in the opposite arm of the cross or chamber, with eachscintillator attached to its own push-pull linear positioner, andwherein the first and second scintillators do not have to be identicaleither in composition or in thickness.
 16. The ionizing-radiationbeamline monitoring system of claim 15, wherein at least one gate valveis positioned between at least one of the scintillator arms and theflange connected to the main body of the cross or vacuum chamber suchthat the gate valve can be closed to allow replacement of thescintillator or scintillators without breaking vacuum in the main bodyof the cross or vacuum chamber or beamline.
 17. The ionizing-radiationbeamline monitoring system of claim 1, wherein the scintillator film inthe beam path comprises a small area of a much larger roll-to-rollscintillator feed system in which the scintillator film is wrappedaround and stored on a small diameter feeder-spool located inside thevacuum chamber structure and pulled across an incidentionizing-radiation beam axis transit area onto a take-up spool that canbe advanced by a stepper-motor rotating a take-up spool spindle to movea new section of scintillator film across the beam axis transit area toreplace a previously radiation damaged area as required.
 18. Theionizing-radiation beamline monitoring system of claim 17, wherein afilm of the scintillator is comprised of biaxially-oriented polyethylenenaphthalate (BoPEN).
 19. The ionizing-radiation beamline monitoringsystem of claim 17, wherein an entire roll-to-roll scintillator feederspool and take-up spool system can be mechanically translated into orout of an incident ionizing-radiation beam transit area without breakingvacuum.
 20. The ionizing-radiation beamline monitoring system of claim1, wherein the machine vision camera is partially shielded from externalradiation by extending the optical tube length of the camera system fromthe beamline and partially compensating for the associated light loss byintroduction of a relay lens system.
 21. The ionizing-radiation beamlinemonitoring system of claim 1, wherein the machine vision camera ispartially shielded from external radiation by being partly enclosedwithin an outer layer or housing of suitable shielding material(s) forattenuating the external radiation of primary concern.
 22. A method ofmonitoring a beam of ionizing-radiation in a vacuum beamline inreal-time, the method comprising: receiving the ionizing-radiation beamin a scintillator enclosed in a vacuum chamber structure with vacuumcompatible flanges through which an incident ionizing-radiation beamenters the vacuum chamber structure, the vacuum chamber structurecomprising a machine vision camera attached to the vacuum chamberstructure; with at least one UV illumination source facing thescintillator; wherein a multitude of emitting photons are created by theionizing-radiation beam passing through the scintillator, some of whichemitted photons are captured by the camera; causing a train of imagedata frames streaming out from the camera to a computer system; whereinthe computer system processes and analyzes the image data streaming fromthe camera in real-time to monitor the beam position, intensity profileand/or shape, beam fluence, and/or a position of single particles.